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2024-02-13xen/events: close evtchn after mapping cleanupMaximilian Heyne1-2/+6
shutdown_pirq and startup_pirq are not taking the irq_mapping_update_lock because they can't due to lock inversion. Both are called with the irq_desc->lock being taking. The lock order, however, is first irq_mapping_update_lock and then irq_desc->lock. This opens multiple races: - shutdown_pirq can be interrupted by a function that allocates an event channel: CPU0 CPU1 shutdown_pirq { xen_evtchn_close(e) __startup_pirq { EVTCHNOP_bind_pirq -> returns just freed evtchn e set_evtchn_to_irq(e, irq) } xen_irq_info_cleanup() { set_evtchn_to_irq(e, -1) } } Assume here event channel e refers here to the same event channel number. After this race the evtchn_to_irq mapping for e is invalid (-1). - __startup_pirq races with __unbind_from_irq in a similar way. Because __startup_pirq doesn't take irq_mapping_update_lock it can grab the evtchn that __unbind_from_irq is currently freeing and cleaning up. In this case even though the event channel is allocated, its mapping can be unset in evtchn_to_irq. The fix is to first cleanup the mappings and then close the event channel. In this way, when an event channel gets allocated it's potential previous evtchn_to_irq mappings are guaranteed to be unset already. This is also the reverse order of the allocation where first the event channel is allocated and then the mappings are setup. On a 5.10 kernel prior to commit 3fcdaf3d7634 ("xen/events: modify internal [un]bind interfaces"), we hit a BUG like the following during probing of NVMe devices. The issue is that during nvme_setup_io_queues, pci_free_irq is called for every device which results in a call to shutdown_pirq. With many nvme devices it's therefore likely to hit this race during boot because there will be multiple calls to shutdown_pirq and startup_pirq are running potentially in parallel. ------------[ cut here ]------------ blkfront: xvda: barrier or flush: disabled; persistent grants: enabled; indirect descriptors: enabled; bounce buffer: enabled kernel BUG at drivers/xen/events/events_base.c:499! invalid opcode: 0000 [#1] SMP PTI CPU: 44 PID: 375 Comm: kworker/u257:23 Not tainted 5.10.201-191.748.amzn2.x86_64 #1 Hardware name: Xen HVM domU, BIOS 4.11.amazon 08/24/2006 Workqueue: nvme-reset-wq nvme_reset_work RIP: 0010:bind_evtchn_to_cpu+0xdf/0xf0 Code: 5d 41 5e c3 cc cc cc cc 44 89 f7 e8 2b 55 ad ff 49 89 c5 48 85 c0 0f 84 64 ff ff ff 4c 8b 68 30 41 83 fe ff 0f 85 60 ff ff ff <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 0f 1f 44 00 00 RSP: 0000:ffffc9000d533b08 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000006 RDX: 0000000000000028 RSI: 00000000ffffffff RDI: 00000000ffffffff RBP: ffff888107419680 R08: 0000000000000000 R09: ffffffff82d72b00 R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000001ed R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000002 FS: 0000000000000000(0000) GS:ffff88bc8b500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000002610001 CR4: 00000000001706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? show_trace_log_lvl+0x1c1/0x2d9 ? show_trace_log_lvl+0x1c1/0x2d9 ? set_affinity_irq+0xdc/0x1c0 ? __die_body.cold+0x8/0xd ? die+0x2b/0x50 ? do_trap+0x90/0x110 ? bind_evtchn_to_cpu+0xdf/0xf0 ? do_error_trap+0x65/0x80 ? bind_evtchn_to_cpu+0xdf/0xf0 ? exc_invalid_op+0x4e/0x70 ? bind_evtchn_to_cpu+0xdf/0xf0 ? asm_exc_invalid_op+0x12/0x20 ? bind_evtchn_to_cpu+0xdf/0xf0 ? bind_evtchn_to_cpu+0xc5/0xf0 set_affinity_irq+0xdc/0x1c0 irq_do_set_affinity+0x1d7/0x1f0 irq_setup_affinity+0xd6/0x1a0 irq_startup+0x8a/0xf0 __setup_irq+0x639/0x6d0 ? nvme_suspend+0x150/0x150 request_threaded_irq+0x10c/0x180 ? nvme_suspend+0x150/0x150 pci_request_irq+0xa8/0xf0 ? __blk_mq_free_request+0x74/0xa0 queue_request_irq+0x6f/0x80 nvme_create_queue+0x1af/0x200 nvme_create_io_queues+0xbd/0xf0 nvme_setup_io_queues+0x246/0x320 ? nvme_irq_check+0x30/0x30 nvme_reset_work+0x1c8/0x400 process_one_work+0x1b0/0x350 worker_thread+0x49/0x310 ? process_one_work+0x350/0x350 kthread+0x11b/0x140 ? __kthread_bind_mask+0x60/0x60 ret_from_fork+0x22/0x30 Modules linked in: ---[ end trace a11715de1eee1873 ]--- Fixes: d46a78b05c0e ("xen: implement pirq type event channels") Cc: stable@vger.kernel.org Co-debugged-by: Andrew Panyakin <apanyaki@amazon.com> Signed-off-by: Maximilian Heyne <mheyne@amazon.de> Reviewed-by: Juergen Gross <jgross@suse.com> Link: https://lore.kernel.org/r/20240124163130.31324-1-mheyne@amazon.de Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-28xen/events: fix error code in xen_bind_pirq_msi_to_irq()Dan Carpenter1-1/+3
Return -ENOMEM if xen_irq_init() fails. currently the code returns an uninitialized variable or zero. Fixes: 5dd9ad32d775 ("xen/events: drop xen_allocate_irqs_dynamic()") Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org> Reviewed-by: Juergen Gross <jgross@ssue.com> Link: https://lore.kernel.org/r/3b9ab040-a92e-4e35-b687-3a95890a9ace@moroto.mountain Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-15xen/events: remove some info_for_irq() calls in pirq handlingJuergen Gross1-49/+68
Instead of the IRQ number user the struct irq_info pointer as parameter in the internal pirq related functions. This allows to drop some calls of info_for_irq(). Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-15xen/events: modify internal [un]bind interfacesJuergen Gross1-135/+124
Modify the internal bind- and unbind-interfaces to take a struct irq_info parameter. When allocating a new IRQ pass the pointer from the allocating function further up. This will reduce the number of info_for_irq() calls and make the code more efficient. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-15xen/events: drop xen_allocate_irqs_dynamic()Juergen Gross1-30/+44
Instead of having a common function for allocating a single IRQ or a consecutive number of IRQs, split up the functionality into the callers of xen_allocate_irqs_dynamic(). This allows to handle any allocation error in xen_irq_init() gracefully instead of panicing the system. Let xen_irq_init() return the irq_info pointer or NULL in case of an allocation error. Additionally set the IRQ into irq_info already at allocation time, as otherwise the IRQ would be '0' (which is a valid IRQ number) until being set. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-14xen/events: remove some simple helpers from events_base.cJuergen Gross1-59/+38
The helper functions type_from_irq() and cpu_from_irq() are just one line functions used only internally. Open code them where needed. At the same time modify and rename get_evtchn_to_irq() to return a struct irq_info instead of the IRQ number. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-14xen/events: reduce externally visible helper functionsJuergen Gross3-9/+13
get_evtchn_to_irq() has only one external user while irq_from_evtchn() provides the same functionality and is exported for a wider user base. Modify the only external user of get_evtchn_to_irq() to use irq_from_evtchn() instead and make get_evtchn_to_irq() static. evtchn_from_irq() and irq_from_virq() have a single external user and can easily be combined to a new helper irq_evtchn_from_virq() allowing to drop irq_from_virq() and to make evtchn_from_irq() static. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-13xen/events: remove unused functionsJuergen Gross1-30/+0
There are no users of xen_irq_from_pirq() and xen_set_irq_pending(). Remove those functions. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-13xen/events: fix delayed eoi list handlingJuergen Gross1-1/+3
When delaying eoi handling of events, the related elements are queued into the percpu lateeoi list. In case the list isn't empty, the elements should be sorted by the time when eoi handling is to happen. Unfortunately a new element will never be queued at the start of the list, even if it has a handling time lower than all other list elements. Fix that by handling that case the same way as for an empty list. Fixes: e99502f76271 ("xen/events: defer eoi in case of excessive number of events") Reported-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-13xen/events: avoid using info_for_irq() in xen_send_IPI_one()Juergen Gross1-4/+8
xen_send_IPI_one() is being used by cpuhp_report_idle_dead() after it calls rcu_report_dead(), meaning that any RCU usage by xen_send_IPI_one() is a bad idea. Unfortunately xen_send_IPI_one() is using notify_remote_via_irq() today, which is using irq_get_chip_data() via info_for_irq(). And irq_get_chip_data() in turn is using a maple-tree lookup requiring RCU. Avoid this problem by caching the ipi event channels in another percpu variable, allowing the use notify_remote_via_evtchn() in xen_send_IPI_one(). Fixes: 721255b9826b ("genirq: Use a maple tree for interrupt descriptor management") Reported-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Juergen Gross <jgross@suse.com> Tested-by: David Woodhouse <dwmw@amazon.co.uk> Acked-by: Stefano Stabellini <sstabellini@kernel.org> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-11-01Merge tag 'for-linus-6.7-rc1-tag' of ↵Linus Torvalds1-1/+2
git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip Pull xen updates from Juergen Gross: - two small cleanup patches - a fix for PCI passthrough under Xen - a four patch series speeding up virtio under Xen with user space backends * tag 'for-linus-6.7-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: xen-pciback: Consider INTx disabled when MSI/MSI-X is enabled xen: privcmd: Add support for ioeventfd xen: evtchn: Allow shared registration of IRQ handers xen: irqfd: Use _IOW instead of the internal _IOC() macro xen: Make struct privcmd_irqfd's layout architecture independent xen/xenbus: Add __counted_by for struct read_buffer and use struct_size() xenbus: fix error exit in xenbus_init()
2023-10-31Merge tag 'locking-core-2023-10-28' of ↵Linus Torvalds1-14/+12
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking updates from Info Molnar: "Futex improvements: - Add the 'futex2' syscall ABI, which is an attempt to get away from the multiplex syscall and adds a little room for extentions, while lifting some limitations. - Fix futex PI recursive rt_mutex waiter state bug - Fix inter-process shared futexes on no-MMU systems - Use folios instead of pages Micro-optimizations of locking primitives: - Improve arch_spin_value_unlocked() on asm-generic ticket spinlock architectures, to improve lockref code generation - Improve the x86-32 lockref_get_not_zero() main loop by adding build-time CMPXCHG8B support detection for the relevant lockref code, and by better interfacing the CMPXCHG8B assembly code with the compiler - Introduce arch_sync_try_cmpxchg() on x86 to improve sync_try_cmpxchg() code generation. Convert some sync_cmpxchg() users to sync_try_cmpxchg(). - Micro-optimize rcuref_put_slowpath() Locking debuggability improvements: - Improve CONFIG_DEBUG_RT_MUTEXES=y to have a fast-path as well - Enforce atomicity of sched_submit_work(), which is de-facto atomic but was un-enforced previously. - Extend <linux/cleanup.h>'s no_free_ptr() with __must_check semantics - Fix ww_mutex self-tests - Clean up const-propagation in <linux/seqlock.h> and simplify the API-instantiation macros a bit RT locking improvements: - Provide the rt_mutex_*_schedule() primitives/helpers and use them in the rtmutex code to avoid recursion vs. rtlock on the PI state. - Add nested blocking lockdep asserts to rt_mutex_lock(), rtlock_lock() and rwbase_read_lock() .. plus misc fixes & cleanups" * tag 'locking-core-2023-10-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits) futex: Don't include process MM in futex key on no-MMU locking/seqlock: Fix grammar in comment alpha: Fix up new futex syscall numbers locking/seqlock: Propagate 'const' pointers within read-only methods, remove forced type casts locking/lockdep: Fix string sizing bug that triggers a format-truncation compiler-warning locking/seqlock: Change __seqprop() to return the function pointer locking/seqlock: Simplify SEQCOUNT_LOCKNAME() locking/atomics: Use atomic_try_cmpxchg_release() to micro-optimize rcuref_put_slowpath() locking/atomic, xen: Use sync_try_cmpxchg() instead of sync_cmpxchg() locking/atomic/x86: Introduce arch_sync_try_cmpxchg() locking/atomic: Add generic support for sync_try_cmpxchg() and its fallback locking/seqlock: Fix typo in comment futex/requeue: Remove unnecessary ‘NULL’ initialization from futex_proxy_trylock_atomic() locking/local, arch: Rewrite local_add_unless() as a static inline function locking/debug: Fix debugfs API return value checks to use IS_ERR() locking/ww_mutex/test: Make sure we bail out instead of livelock locking/ww_mutex/test: Fix potential workqueue corruption locking/ww_mutex/test: Use prng instead of rng to avoid hangs at bootup futex: Add sys_futex_requeue() futex: Add flags2 argument to futex_requeue() ...
2023-10-16xen: evtchn: Allow shared registration of IRQ handersViresh Kumar1-1/+2
Currently the handling of events is supported either in the kernel or userspace, but not both. In order to support fast delivery of interrupts from the guest to the backend, we need to handle the Queue notify part of Virtio protocol in kernel and the rest in userspace. Update the interrupt handler registration flag to IRQF_SHARED for event channels, which would allow multiple entities to bind their interrupt handler for the same event channel port. Also increment the reference count of irq_info when multiple entities try to bind event channel to irqchip, so the unbinding happens only after all the users are gone. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Juergen Gross <jgross@suse.com> Link: https://lore.kernel.org/r/99b1edfd3147c6b5d22a5139dab5861e767dc34a.1697439990.git.viresh.kumar@linaro.org Signed-off-by: Juergen Gross <jgross@suse.com>
2023-10-09locking/atomic, xen: Use sync_try_cmpxchg() instead of sync_cmpxchg()Uros Bizjak1-14/+12
Use sync_try_cmpxchg() instead of sync_cmpxchg(*ptr, old, new) == old in clear_masked_cond(), clear_linked() and gnttab_end_foreign_access_ref_v1(). x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg), improving the cmpxchg loop in gnttab_end_foreign_access_ref_v1() from: 174: eb 0e jmp 184 <...> 176: 89 d0 mov %edx,%eax 178: f0 66 0f b1 31 lock cmpxchg %si,(%rcx) 17d: 66 39 c2 cmp %ax,%dx 180: 74 11 je 193 <...> 182: 89 c2 mov %eax,%edx 184: 89 d6 mov %edx,%esi 186: 66 83 e6 18 and $0x18,%si 18a: 74 ea je 176 <...> to: 614: 89 c1 mov %eax,%ecx 616: 66 83 e1 18 and $0x18,%cx 61a: 75 11 jne 62d <...> 61c: f0 66 0f b1 0a lock cmpxchg %cx,(%rdx) 621: 75 f1 jne 614 <...> No functional change intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Juergen Gross <jgross@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-kernel@vger.kernel.org
2023-10-09xen/events: replace evtchn_rwlock with RCUJuergen Gross1-41/+46
In unprivileged Xen guests event handling can cause a deadlock with Xen console handling. The evtchn_rwlock and the hvc_lock are taken in opposite sequence in __hvc_poll() and in Xen console IRQ handling. Normally this is no problem, as the evtchn_rwlock is taken as a reader in both paths, but as soon as an event channel is being closed, the lock will be taken as a writer, which will cause read_lock() to block: CPU0 CPU1 CPU2 (IRQ handling) (__hvc_poll()) (closing event channel) read_lock(evtchn_rwlock) spin_lock(hvc_lock) write_lock(evtchn_rwlock) [blocks] spin_lock(hvc_lock) [blocks] read_lock(evtchn_rwlock) [blocks due to writer waiting, and not in_interrupt()] This issue can be avoided by replacing evtchn_rwlock with RCU in xen_free_irq(). Note that RCU is used only to delay freeing of the irq_info memory. There is no RCU based dereferencing or replacement of pointers involved. In order to avoid potential races between removing the irq_info reference and handling of interrupts, set the irq_info pointer to NULL only when freeing its memory. The IRQ itself must be freed at that time, too, as otherwise the same IRQ number could be allocated again before handling of the old instance would have been finished. This is XSA-441 / CVE-2023-34324. Fixes: 54c9de89895e ("xen/events: add a new "late EOI" evtchn framework") Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Julien Grall <jgrall@amazon.com> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-09-19xen: simplify evtchn_do_upcall() call mazeJuergen Gross1-19/+2
There are several functions involved for performing the functionality of evtchn_do_upcall(): - __xen_evtchn_do_upcall() doing the real work - xen_hvm_evtchn_do_upcall() just being a wrapper for __xen_evtchn_do_upcall(), exposed for external callers - xen_evtchn_do_upcall() calling __xen_evtchn_do_upcall(), too, but without any user Simplify this maze by: - removing the unused xen_evtchn_do_upcall() - removing xen_hvm_evtchn_do_upcall() as the only left caller of __xen_evtchn_do_upcall(), while renaming __xen_evtchn_do_upcall() to xen_evtchn_do_upcall() Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Juergen Gross <jgross@suse.com>
2023-07-26xen/evtchn: Introduce new IOCTL to bind static evtchnRahul Singh1-11/+5
Xen 4.17 supports the creation of static evtchns. To allow user space application to bind static evtchns introduce new ioctl "IOCTL_EVTCHN_BIND_STATIC". Existing IOCTL doing more than binding that’s why we need to introduce the new IOCTL to only bind the static event channels. Static evtchns to be available for use during the lifetime of the guest. When the application exits, __unbind_from_irq() ends up being called from release() file operations because of that static evtchns are getting closed. To avoid closing the static event channel, add the new bool variable "is_static" in "struct irq_info" to mark the event channel static when creating the event channel to avoid closing the static evtchn. Also, take this opportunity to remove the open-coded version of the evtchn close in drivers/xen/evtchn.c file and use xen_evtchn_close(). Signed-off-by: Rahul Singh <rahul.singh@arm.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Acked-by: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/ae7329bf1713f83e4aad4f3fa0f316258c40a3e9.1689677042.git.rahul.singh@arm.com Signed-off-by: Juergen Gross <jgross@suse.com>
2023-02-13xen: Allow platform PCI interrupt to be sharedDavid Woodhouse1-3/+6
When we don't use the per-CPU vector callback, we ask Xen to deliver event channel interrupts as INTx on the PCI platform device. As such, it can be shared with INTx on other PCI devices. Set IRQF_SHARED, and make it return IRQ_HANDLED or IRQ_NONE according to whether the evtchn_upcall_pending flag was actually set. Now I can share the interrupt: 11: 82 0 IO-APIC 11-fasteoi xen-platform-pci, ens4 Drop the IRQF_TRIGGER_RISING. It has no effect when the IRQ is shared, and besides, the only effect it was having even beforehand was to trigger a debug message in both I/OAPIC and legacy PIC cases: [ 0.915441] genirq: No set_type function for IRQ 11 (IO-APIC) [ 0.951939] genirq: No set_type function for IRQ 11 (XT-PIC) Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Juergen Gross <jgross@suse.com> Link: https://lore.kernel.org/r/f9a29a68d05668a3636dd09acd94d970269eaec6.camel@infradead.org Signed-off-by: Juergen Gross <jgross@suse.com>
2022-08-14Merge tag 'for-linus-6.0-rc1b-tag' of ↵Linus Torvalds1-6/+47
git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip Pull more xen updates from Juergen Gross: - fix the handling of the "persistent grants" feature negotiation between Xen blkfront and Xen blkback drivers - a cleanup of xen.config and adding xen.config to Xen section in MAINTAINERS - support HVMOP_set_evtchn_upcall_vector, which is more compliant to "normal" interrupt handling than the global callback used up to now - further small cleanups * tag 'for-linus-6.0-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: MAINTAINERS: add xen config fragments to XEN HYPERVISOR sections xen: remove XEN_SCRUB_PAGES in xen.config xen/pciback: Fix comment typo xen/xenbus: fix return type in xenbus_file_read() xen-blkfront: Apply 'feature_persistent' parameter when connect xen-blkback: Apply 'feature_persistent' parameter when connect xen-blkback: fix persistent grants negotiation x86/xen: Add support for HVMOP_set_evtchn_upcall_vector
2022-08-12x86/xen: Add support for HVMOP_set_evtchn_upcall_vectorJane Malalane1-6/+47
Implement support for the HVMOP_set_evtchn_upcall_vector hypercall in order to set the per-vCPU event channel vector callback on Linux and use it in preference of HVM_PARAM_CALLBACK_IRQ. If the per-VCPU vector setup is successful on BSP, use this method for the APs. If not, fallback to the global vector-type callback. Also register callback_irq at per-vCPU event channel setup to trick toolstack to think the domain is enlightened. Suggested-by: "Roger Pau Monné" <roger.pau@citrix.com> Signed-off-by: Jane Malalane <jane.malalane@citrix.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: https://lore.kernel.org/r/20220729070416.23306-1-jane.malalane@citrix.com Signed-off-by: Juergen Gross <jgross@suse.com>
2022-07-07genirq: Add and use an irq_data_update_affinity helperSamuel Holland1-3/+4
Some architectures and irqchip drivers modify the cpumask returned by irq_data_get_affinity_mask, usually by copying in to it. This is problematic for uniprocessor configurations, where the affinity mask should be constant, as it is known at compile time. Add and use a setter for the affinity mask, following the pattern of irq_data_update_effective_affinity. This allows the getter function to return a const cpumask pointer. Signed-off-by: Samuel Holland <samuel@sholland.org> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Xen bits Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220701200056.46555-7-samuel@sholland.org
2021-12-16xen/console: harden hvc_xen against event channel stormsJuergen Gross1-0/+6
The Xen console driver is still vulnerable for an attack via excessive number of events sent by the backend. Fix that by using a lateeoi event channel. For the normal domU initial console this requires the introduction of bind_evtchn_to_irq_lateeoi() as there is no xenbus device available at the time the event channel is bound to the irq. As the decision whether an interrupt was spurious or not requires to test for bytes having been read from the backend, move sending the event into the if statement, as sending an event without having found any bytes to be read is making no sense at all. This is part of XSA-391 Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> --- V2: - slightly adapt spurious irq detection (Jan Beulich) V3: - fix spurious irq detection (Jan Beulich)
2021-08-12xen/events: Fix race in set_evtchn_to_irqMaximilian Heyne1-6/+14
There is a TOCTOU issue in set_evtchn_to_irq. Rows in the evtchn_to_irq mapping are lazily allocated in this function. The check whether the row is already present and the row initialization is not synchronized. Two threads can at the same time allocate a new row for evtchn_to_irq and add the irq mapping to the their newly allocated row. One thread will overwrite what the other has set for evtchn_to_irq[row] and therefore the irq mapping is lost. This will trigger a BUG_ON later in bind_evtchn_to_cpu: INFO: pci 0000:1a:15.4: [1d0f:8061] type 00 class 0x010802 INFO: nvme 0000:1a:12.1: enabling device (0000 -> 0002) INFO: nvme nvme77: 1/0/0 default/read/poll queues CRIT: kernel BUG at drivers/xen/events/events_base.c:427! WARN: invalid opcode: 0000 [#1] SMP NOPTI WARN: Workqueue: nvme-reset-wq nvme_reset_work [nvme] WARN: RIP: e030:bind_evtchn_to_cpu+0xc2/0xd0 WARN: Call Trace: WARN: set_affinity_irq+0x121/0x150 WARN: irq_do_set_affinity+0x37/0xe0 WARN: irq_setup_affinity+0xf6/0x170 WARN: irq_startup+0x64/0xe0 WARN: __setup_irq+0x69e/0x740 WARN: ? request_threaded_irq+0xad/0x160 WARN: request_threaded_irq+0xf5/0x160 WARN: ? nvme_timeout+0x2f0/0x2f0 [nvme] WARN: pci_request_irq+0xa9/0xf0 WARN: ? pci_alloc_irq_vectors_affinity+0xbb/0x130 WARN: queue_request_irq+0x4c/0x70 [nvme] WARN: nvme_reset_work+0x82d/0x1550 [nvme] WARN: ? check_preempt_wakeup+0x14f/0x230 WARN: ? check_preempt_curr+0x29/0x80 WARN: ? nvme_irq_check+0x30/0x30 [nvme] WARN: process_one_work+0x18e/0x3c0 WARN: worker_thread+0x30/0x3a0 WARN: ? process_one_work+0x3c0/0x3c0 WARN: kthread+0x113/0x130 WARN: ? kthread_park+0x90/0x90 WARN: ret_from_fork+0x3a/0x50 This patch sets evtchn_to_irq rows via a cmpxchg operation so that they will be set only once. The row is now cleared before writing it to evtchn_to_irq in order to not create a race once the row is visible for other threads. While at it, do not require the page to be zeroed, because it will be overwritten with -1's in clear_evtchn_to_irq_row anyway. Signed-off-by: Maximilian Heyne <mheyne@amazon.de> Fixes: d0b075ffeede ("xen/events: Refactor evtchn_to_irq array to be dynamically allocated") Link: https://lore.kernel.org/r/20210812130930.127134-1-mheyne@amazon.de Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2021-07-21xen/events: remove redundant initialization of variable irqColin Ian King1-1/+1
The variable irq is being initialized with a value that is never read, it is being updated later on. The assignment is redundant and can be removed. Addresses-Coverity: ("Unused value") Signed-off-by: Colin Ian King <colin.king@canonical.com> Link: https://lore.kernel.org/r/20210721114010.108648-1-colin.king@canonical.com Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2021-06-24xen/events: reset active flag for lateeoi events laterJuergen Gross1-1/+10
In order to avoid a race condition for user events when changing cpu affinity reset the active flag only when EOI-ing the event. This is working fine as all user events are lateeoi events. Note that lateeoi_ack_mask_dynirq() is not modified as there is no explicit call to xen_irq_lateeoi() expected later. Cc: stable@vger.kernel.org Reported-by: Julien Grall <julien@xen.org> Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time") Tested-by: Julien Grall <julien@xen.org> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com> Link: https://lore.kernel.org/r/20210623130913.9405-1-jgross@suse.com Signed-off-by: Juergen Gross <jgross@suse.com>
2021-04-07xen/evtchn: Change irq_info lock to raw_spinlock_tLuca Fancellu1-6/+6
Unmask operation must be called with interrupt disabled, on preempt_rt spin_lock_irqsave/spin_unlock_irqrestore don't disable/enable interrupts, so use raw_* implementation and change lock variable in struct irq_info from spinlock_t to raw_spinlock_t Cc: stable@vger.kernel.org Fixes: 25da4618af24 ("xen/events: don't unmask an event channel when an eoi is pending") Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> Reviewed-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Wei Liu <wei.liu@kernel.org> Link: https://lore.kernel.org/r/20210406105105.10141-1-luca.fancellu@arm.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2021-03-11xen/events: avoid handling the same event on two cpus at the same timeJuergen Gross1-11/+21
When changing the cpu affinity of an event it can happen today that (with some unlucky timing) the same event will be handled on the old and the new cpu at the same time. Avoid that by adding an "event active" flag to the per-event data and call the handler only if this flag isn't set. Cc: stable@vger.kernel.org Reported-by: Julien Grall <julien@xen.org> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Julien Grall <jgrall@amazon.com> Link: https://lore.kernel.org/r/20210306161833.4552-4-jgross@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2021-03-11xen/events: don't unmask an event channel when an eoi is pendingJuergen Gross4-41/+80
An event channel should be kept masked when an eoi is pending for it. When being migrated to another cpu it might be unmasked, though. In order to avoid this keep three different flags for each event channel to be able to distinguish "normal" masking/unmasking from eoi related masking/unmasking and temporary masking. The event channel should only be able to generate an interrupt if all flags are cleared. Cc: stable@vger.kernel.org Fixes: 54c9de89895e ("xen/events: add a new "late EOI" evtchn framework") Reported-by: Julien Grall <julien@xen.org> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Tested-by: Ross Lagerwall <ross.lagerwall@citrix.com> Link: https://lore.kernel.org/r/20210306161833.4552-3-jgross@suse.com [boris -- corrected Fixed tag format] Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2021-03-10xen/events: reset affinity of 2-level event when tearing it downJuergen Gross3-0/+24
When creating a new event channel with 2-level events the affinity needs to be reset initially in order to avoid using an old affinity from earlier usage of the event channel port. So when tearing an event channel down reset all affinity bits. The same applies to the affinity when onlining a vcpu: all old affinity settings for this vcpu must be reset. As percpu events get initialized before the percpu event channel hook is called, resetting of the affinities happens after offlining a vcpu (this is working, as initial percpu memory is zeroed out). Cc: stable@vger.kernel.org Reported-by: Julien Grall <julien@xen.org> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Julien Grall <jgrall@amazon.com> Link: https://lore.kernel.org/r/20210306161833.4552-2-jgross@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2021-02-23xen/events: add per-xenbus device event statistics and settingsJuergen Gross1-2/+25
Add syfs nodes for each xenbus device showing event statistics (number of events and spurious events, number of associated event channels) and for setting a spurious event threshold in case a frontend is sending too many events without being rogue on purpose. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: https://lore.kernel.org/r/20210219154030.10892-7-jgross@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2021-02-12xen/events: link interdomain events to associated xenbus deviceJuergen Gross1-17/+24
In order to support the possibility of per-device event channel settings (e.g. lateeoi spurious event thresholds) add a xenbus device pointer to struct irq_info() and modify the related event channel binding interfaces to take the pointer to the xenbus device as a parameter instead of the domain id of the other side. While at it remove the stale prototype of bind_evtchn_to_irq_lateeoi(). Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Reviewed-by: Wei Liu <wei.liu@kernel.org> Reviewed-by: Paul Durrant <paul@xen.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2021-01-15Merge tag 'for-linus-5.11-rc4-tag' of ↵Linus Torvalds1-10/+0
git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip Pull xen fixes from Juergen Gross: - A series to fix a regression when running as a fully virtualized guest on an old Xen hypervisor not supporting PV interrupt callbacks for HVM guests. - A patch to add support to query Xen resource sizes (setting was possible already) from user mode. * tag 'for-linus-5.11-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: x86/xen: Fix xen_hvm_smp_init() when vector callback not available x86/xen: Don't register Xen IPIs when they aren't going to be used x86/xen: Add xen_no_vector_callback option to test PCI INTX delivery xen: Set platform PCI device INTX affinity to CPU0 xen: Fix event channel callback via INTX/GSI xen/privcmd: allow fetching resource sizes
2021-01-13xen: Fix event channel callback via INTX/GSIDavid Woodhouse1-10/+0
For a while, event channel notification via the PCI platform device has been broken, because we attempt to communicate with xenstore before we even have notifications working, with the xs_reset_watches() call in xs_init(). We tend to get away with this on Xen versions below 4.0 because we avoid calling xs_reset_watches() anyway, because xenstore might not cope with reading a non-existent key. And newer Xen *does* have the vector callback support, so we rarely fall back to INTX/GSI delivery. To fix it, clean up a bit of the mess of xs_init() and xenbus_probe() startup. Call xs_init() directly from xenbus_init() only in the !XS_HVM case, deferring it to be called from xenbus_probe() in the XS_HVM case instead. Then fix up the invocation of xenbus_probe() to happen either from its device_initcall if the callback is available early enough, or when the callback is finally set up. This means that the hack of calling xenbus_probe() from a workqueue after the first interrupt, or directly from the PCI platform device setup, is no longer needed. Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: https://lore.kernel.org/r/20210113132606.422794-2-dwmw2@infradead.org Signed-off-by: Juergen Gross <jgross@suse.com>
2020-12-15xen/events: Implement irq distributionThomas Gleixner1-8/+68
Keep track of the assignments of event channels to CPUs and select the online CPU with the least assigned channels in the affinity mask which is handed to irq_chip::irq_set_affinity() from the core code. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/20201210194045.457218278@linutronix.de
2020-12-15xen/events: Reduce irq_info:: Spurious_cnt storage sizeThomas Gleixner1-3/+5
To prepare for interrupt spreading reduce the storage size of irq_info::spurious_cnt to u8 so the required flag for the spreading logic will not increase the storage size. Protect the usage site against overruns. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/20201210194045.360198201@linutronix.de
2020-12-15xen/events: Only force affinity mask for percpu interruptsThomas Gleixner1-14/+34
All event channel setups bind the interrupt on CPU0 or the target CPU for percpu interrupts and overwrite the affinity mask with the corresponding cpumask. That does not make sense. The XEN implementation of irqchip::irq_set_affinity() already picks a single target CPU out of the affinity mask and the actual target is stored in the effective CPU mask, so destroying the user chosen affinity mask which might contain more than one CPU is wrong. Change the implementation so that the channel is bound to CPU0 at the XEN level and leave the affinity mask alone. At startup of the interrupt affinity will be assigned out of the affinity mask and the XEN binding will be updated. Only keep the enforcement for real percpu interrupts. On resume the overwrite is not required either because info->cpu and the affinity mask are still the same as at the time of suspend. Same for rebind_evtchn_irq(). This also prepares for proper interrupt spreading. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/20201210194045.250321315@linutronix.de
2020-12-15xen/events: Use immediate affinity settingThomas Gleixner1-26/+9
There is absolutely no reason to mimic the x86 deferred affinity setting. This mechanism is required to handle the hardware induced issues of IO/APIC and MSI and is not in use when the interrupts are remapped. XEN does not need this and can simply change the affinity from the calling context. The core code invokes this with the interrupt descriptor lock held so it is fully serialized against any other operation. Mark the interrupts with IRQ_MOVE_PCNTXT to disable the deferred affinity setting. The conditional mask/unmask operation is already handled in xen_rebind_evtchn_to_cpu(). This makes XEN on x86 use the same mechanics as on e.g. ARM64 where deferred affinity setting is not required and not implemented and the code path in the ack functions is compiled out. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/20201210194045.157601122@linutronix.de
2020-12-15xen/events: Remove disfunct affinity spreadingThomas Gleixner1-9/+0
This function can only ever work when the event channels: - are already established - interrupts assigned to them - the affinity has been set by user space already because any newly set up event channel is forced to be bound to CPU0 and the affinity mask of the interrupt is forced to contain cpumask_of(0). As the CPU0 enforcement was in place _before_ this was implemented it's entirely unclear how that can ever have worked at all. Remove it as preparation for doing it proper. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/20201210194045.065115500@linutronix.de
2020-12-15xen/events: Remove unused bind_evtchn_to_irq_lateeoi()Thomas Gleixner1-6/+0
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/20201210194044.972064156@linutronix.de
2020-10-23xen/events: unmask a fifo event channel only if it was maskedJuergen Gross1-0/+3
Unmasking an event channel with fifo events channels being used can require a hypercall to be made, so try to avoid that by checking whether the event channel was really masked. Suggested-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Link: https://lore.kernel.org/r/20201022094907.28560-5-jgross@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2020-10-23xen/events: only register debug interrupt for 2-level eventsJuergen Gross1-4/+6
xen_debug_interrupt() is specific to 2-level event handling. So don't register it with fifo event handling being active. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Link: https://lore.kernel.org/r/20201022094907.28560-4-jgross@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2020-10-23xen/events: make struct irq_info private to events_base.cJuergen Gross4-73/+73
The struct irq_info of Xen's event handling is used only for two evtchn_ops functions outside of events_base.c. Those two functions can easily be switched to avoid that usage. This allows to make struct irq_info and its related access functions private to events_base.c. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Link: https://lore.kernel.org/r/20201022094907.28560-3-jgross@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2020-10-23xen: remove no longer used functionsJuergen Gross1-21/+0
With the switch to the lateeoi model for interdomain event channels some functions are no longer in use. Remove them. Suggested-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Link: https://lore.kernel.org/r/20201022094907.28560-2-jgross@suse.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2020-10-20xen/events: block rogue events for some timeJuergen Gross2-6/+24
In order to avoid high dom0 load due to rogue guests sending events at high frequency, block those events in case there was no action needed in dom0 to handle the events. This is done by adding a per-event counter, which set to zero in case an EOI without the XEN_EOI_FLAG_SPURIOUS is received from a backend driver, and incremented when this flag has been set. In case the counter is 2 or higher delay the EOI by 1 << (cnt - 2) jiffies, but not more than 1 second. In order not to waste memory shorten the per-event refcnt to two bytes (it should normally never exceed a value of 2). Add an overflow check to evtchn_get() to make sure the 2 bytes really won't overflow. This is part of XSA-332. Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Reviewed-by: Wei Liu <wl@xen.org>
2020-10-20xen/events: defer eoi in case of excessive number of eventsJuergen Gross4-32/+208
In case rogue guests are sending events at high frequency it might happen that xen_evtchn_do_upcall() won't stop processing events in dom0. As this is done in irq handling a crash might be the result. In order to avoid that, delay further inter-domain events after some time in xen_evtchn_do_upcall() by forcing eoi processing into a worker on the same cpu, thus inhibiting new events coming in. The time after which eoi processing is to be delayed is configurable via a new module parameter "event_loop_timeout" which specifies the maximum event loop time in jiffies (default: 2, the value was chosen after some tests showing that a value of 2 was the lowest with an only slight drop of dom0 network throughput while multiple guests performed an event storm). How long eoi processing will be delayed can be specified via another parameter "event_eoi_delay" (again in jiffies, default 10, again the value was chosen after testing with different delay values). This is part of XSA-332. Cc: stable@vger.kernel.org Reported-by: Julien Grall <julien@xen.org> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Reviewed-by: Wei Liu <wl@xen.org>
2020-10-20xen/events: use a common cpu hotplug hook for event channelsJuergen Gross3-21/+47
Today only fifo event channels have a cpu hotplug callback. In order to prepare for more percpu (de)init work move that callback into events_base.c and add percpu_init() and percpu_deinit() hooks to struct evtchn_ops. This is part of XSA-332. Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Wei Liu <wl@xen.org>
2020-10-20xen/events: add a new "late EOI" evtchn frameworkJuergen Gross1-17/+134
In order to avoid tight event channel related IRQ loops add a new framework of "late EOI" handling: the IRQ the event channel is bound to will be masked until the event has been handled and the related driver is capable to handle another event. The driver is responsible for unmasking the event channel via the new function xen_irq_lateeoi(). This is similar to binding an event channel to a threaded IRQ, but without having to structure the driver accordingly. In order to support a future special handling in case a rogue guest is sending lots of unsolicited events, add a flag to xen_irq_lateeoi() which can be set by the caller to indicate the event was a spurious one. This is part of XSA-332. Cc: stable@vger.kernel.org Reported-by: Julien Grall <julien@xen.org> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Reviewed-by: Wei Liu <wl@xen.org>
2020-10-20xen/events: fix race in evtchn_fifo_unmask()Juergen Gross1-4/+9
Unmasking a fifo event channel can result in unmasking it twice, once directly in the kernel and once via a hypercall in case the event was pending. Fix that by doing the local unmask only if the event is not pending. This is part of XSA-332. Cc: stable@vger.kernel.org Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>
2020-10-20xen/events: add a proper barrier to 2-level uevent unmaskingJuergen Gross1-0/+2
A follow-up patch will require certain write to happen before an event channel is unmasked. While the memory barrier is not strictly necessary for all the callers, the main one will need it. In order to avoid an extra memory barrier when using fifo event channels, mandate evtchn_unmask() to provide write ordering. The 2-level event handling unmask operation is missing an appropriate barrier, so add it. Fifo event channels are fine in this regard due to using sync_cmpxchg(). This is part of XSA-332. Cc: stable@vger.kernel.org Suggested-by: Julien Grall <julien@xen.org> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Julien Grall <jgrall@amazon.com> Reviewed-by: Wei Liu <wl@xen.org>
2020-10-20xen/events: avoid removing an event channel while handling itJuergen Gross1-5/+36
Today it can happen that an event channel is being removed from the system while the event handling loop is active. This can lead to a race resulting in crashes or WARN() splats when trying to access the irq_info structure related to the event channel. Fix this problem by using a rwlock taken as reader in the event handling loop and as writer when deallocating the irq_info structure. As the observed problem was a NULL dereference in evtchn_from_irq() make this function more robust against races by testing the irq_info pointer to be not NULL before dereferencing it. And finally make all accesses to evtchn_to_irq[row][col] atomic ones in order to avoid seeing partial updates of an array element in irq handling. Note that irq handling can be entered only for event channels which have been valid before, so any not populated row isn't a problem in this regard, as rows are only ever added and never removed. This is XSA-331. Cc: stable@vger.kernel.org Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Reported-by: Jinoh Kang <luke1337@theori.io> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Reviewed-by: Wei Liu <wl@xen.org>
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