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authorLinus Torvalds <torvalds@linux-foundation.org>2023-01-13 23:41:50 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2023-01-13 23:41:50 +0300
commit92783a90bcbde8659dd4a160506c46c56db494d6 (patch)
tree080a6edd7cf645b404a7b0ea28abba60c2942d16 /Documentation
parentf5fe24ef17b5fbe6db49534163e77499fb10ae8c (diff)
parent310bc39546a435c83cc27a0eba878afac0d74714 (diff)
downloadlinux-92783a90bcbde8659dd4a160506c46c56db494d6.tar.xz
Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fixes from Paolo Bonzini: "ARM: - Fix the PMCR_EL0 reset value after the PMU rework - Correctly handle S2 fault triggered by a S1 page table walk by not always classifying it as a write, as this breaks on R/O memslots - Document why we cannot exit with KVM_EXIT_MMIO when taking a write fault from a S1 PTW on a R/O memslot - Put the Apple M2 on the naughty list for not being able to correctly implement the vgic SEIS feature, just like the M1 before it - Reviewer updates: Alex is stepping down, replaced by Zenghui x86: - Fix various rare locking issues in Xen emulation and teach lockdep to detect them - Documentation improvements - Do not return host topology information from KVM_GET_SUPPORTED_CPUID" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: KVM: x86/xen: Avoid deadlock by adding kvm->arch.xen.xen_lock leaf node lock KVM: Ensure lockdep knows about kvm->lock vs. vcpu->mutex ordering rule KVM: x86/xen: Fix potential deadlock in kvm_xen_update_runstate_guest() KVM: x86/xen: Fix lockdep warning on "recursive" gpc locking Documentation: kvm: fix SRCU locking order docs KVM: x86: Do not return host topology information from KVM_GET_SUPPORTED_CPUID KVM: nSVM: clarify recalc_intercepts() wrt CR8 MAINTAINERS: Remove myself as a KVM/arm64 reviewer MAINTAINERS: Add Zenghui Yu as a KVM/arm64 reviewer KVM: arm64: vgic: Add Apple M2 cpus to the list of broken SEIS implementations KVM: arm64: Convert FSC_* over to ESR_ELx_FSC_* KVM: arm64: Document the behaviour of S1PTW faults on RO memslots KVM: arm64: Fix S1PTW handling on RO memslots KVM: arm64: PMU: Fix PMCR_EL0 reset value
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/virt/kvm/api.rst22
-rw-r--r--Documentation/virt/kvm/locking.rst25
2 files changed, 35 insertions, 12 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index deb494f759ed..9807b05a1b57 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1354,6 +1354,14 @@ the memory region are automatically reflected into the guest. For example, an
mmap() that affects the region will be made visible immediately. Another
example is madvise(MADV_DROP).
+Note: On arm64, a write generated by the page-table walker (to update
+the Access and Dirty flags, for example) never results in a
+KVM_EXIT_MMIO exit when the slot has the KVM_MEM_READONLY flag. This
+is because KVM cannot provide the data that would be written by the
+page-table walker, making it impossible to emulate the access.
+Instead, an abort (data abort if the cause of the page-table update
+was a load or a store, instruction abort if it was an instruction
+fetch) is injected in the guest.
4.36 KVM_SET_TSS_ADDR
---------------------
@@ -8310,6 +8318,20 @@ CPU[EAX=1]:ECX[24] (TSC_DEADLINE) is not reported by ``KVM_GET_SUPPORTED_CPUID``
It can be enabled if ``KVM_CAP_TSC_DEADLINE_TIMER`` is present and the kernel
has enabled in-kernel emulation of the local APIC.
+CPU topology
+~~~~~~~~~~~~
+
+Several CPUID values include topology information for the host CPU:
+0x0b and 0x1f for Intel systems, 0x8000001e for AMD systems. Different
+versions of KVM return different values for this information and userspace
+should not rely on it. Currently they return all zeroes.
+
+If userspace wishes to set up a guest topology, it should be careful that
+the values of these three leaves differ for each CPU. In particular,
+the APIC ID is found in EDX for all subleaves of 0x0b and 0x1f, and in EAX
+for 0x8000001e; the latter also encodes the core id and node id in bits
+7:0 of EBX and ECX respectively.
+
Obsolete ioctls and capabilities
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst
index a3ca76f9be75..a0146793d197 100644
--- a/Documentation/virt/kvm/locking.rst
+++ b/Documentation/virt/kvm/locking.rst
@@ -24,21 +24,22 @@ The acquisition orders for mutexes are as follows:
For SRCU:
-- ``synchronize_srcu(&kvm->srcu)`` is called _inside_
- the kvm->slots_lock critical section, therefore kvm->slots_lock
- cannot be taken inside a kvm->srcu read-side critical section.
- Instead, kvm->slots_arch_lock is released before the call
- to ``synchronize_srcu()`` and _can_ be taken inside a
- kvm->srcu read-side critical section.
-
-- kvm->lock is taken inside kvm->srcu, therefore
- ``synchronize_srcu(&kvm->srcu)`` cannot be called inside
- a kvm->lock critical section. If you cannot delay the
- call until after kvm->lock is released, use ``call_srcu``.
+- ``synchronize_srcu(&kvm->srcu)`` is called inside critical sections
+ for kvm->lock, vcpu->mutex and kvm->slots_lock. These locks _cannot_
+ be taken inside a kvm->srcu read-side critical section; that is, the
+ following is broken::
+
+ srcu_read_lock(&kvm->srcu);
+ mutex_lock(&kvm->slots_lock);
+
+- kvm->slots_arch_lock instead is released before the call to
+ ``synchronize_srcu()``. It _can_ therefore be taken inside a
+ kvm->srcu read-side critical section, for example while processing
+ a vmexit.
On x86:
-- vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock
+- vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock and kvm->arch.xen.xen_lock
- kvm->arch.mmu_lock is an rwlock. kvm->arch.tdp_mmu_pages_lock and
kvm->arch.mmu_unsync_pages_lock are taken inside kvm->arch.mmu_lock, and