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The following panic can happen when mmap is called before the pmu add
callback which sets the hardware counter index: this happens for example
with the following command `perf record --no-bpf-event -n kill`.
[ 99.461486] CPU: 1 PID: 1259 Comm: perf Tainted: G E 6.6.0-rc4ubuntu-defconfig #2
[ 99.461669] Hardware name: riscv-virtio,qemu (DT)
[ 99.461748] epc : pmu_sbi_set_scounteren+0x42/0x44
[ 99.462337] ra : smp_call_function_many_cond+0x126/0x5b0
[ 99.462369] epc : ffffffff809f9d24 ra : ffffffff800f93e0 sp : ff60000082153aa0
[ 99.462407] gp : ffffffff82395c98 tp : ff6000009a218040 t0 : ff6000009ab3a4f0
[ 99.462425] t1 : 0000000000000004 t2 : 0000000000000100 s0 : ff60000082153ab0
[ 99.462459] s1 : 0000000000000000 a0 : ff60000098869528 a1 : 0000000000000000
[ 99.462473] a2 : 000000000000001f a3 : 0000000000f00000 a4 : fffffffffffffff8
[ 99.462488] a5 : 00000000000000cc a6 : 0000000000000000 a7 : 0000000000735049
[ 99.462502] s2 : 0000000000000001 s3 : ffffffff809f9ce2 s4 : ff60000098869528
[ 99.462516] s5 : 0000000000000002 s6 : 0000000000000004 s7 : 0000000000000001
[ 99.462530] s8 : ff600003fec98bc0 s9 : ffffffff826c5890 s10: ff600003fecfcde0
[ 99.462544] s11: ff600003fec98bc0 t3 : ffffffff819e2558 t4 : ff1c000004623840
[ 99.462557] t5 : 0000000000000901 t6 : ff6000008feeb890
[ 99.462570] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
[ 99.462658] [<ffffffff809f9d24>] pmu_sbi_set_scounteren+0x42/0x44
[ 99.462979] Code: 1060 4785 97bb 00d7 8fd9 9073 1067 6422 0141 8082 (9002) 0013
[ 99.463335] Kernel BUG [#2]
To circumvent this, try to enable userspace access to the hardware counter
when it is selected in addition to when the event is mapped. And vice-versa
when the event is stopped/unmapped.
Fixes: cc4c07c89aad ("drivers: perf: Implement perf event mmap support in the SBI backend")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20231006082010.11963-1-alexghiti@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux
Pull RISC-V updates from Palmer Dabbelt:
- Support for the new "riscv,isa-extensions" and "riscv,isa-base"
device tree interfaces for probing extensions
- Support for userspace access to the performance counters
- Support for more instructions in kprobes
- Crash kernels can be allocated above 4GiB
- Support for KCFI
- Support for ELFs in !MMU configurations
- ARCH_KMALLOC_MINALIGN has been reduced to 8
- mmap() defaults to sv48-sized addresses, with longer addresses hidden
behind a hint (similar to Arm and Intel)
- Also various fixes and cleanups
* tag 'riscv-for-linus-6.6-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (51 commits)
lib/Kconfig.debug: Restrict DEBUG_INFO_SPLIT for RISC-V
riscv: support PREEMPT_DYNAMIC with static keys
riscv: Move create_tmp_mapping() to init sections
riscv: Mark KASAN tmp* page tables variables as static
riscv: mm: use bitmap_zero() API
riscv: enable DEBUG_FORCE_FUNCTION_ALIGN_64B
riscv: remove redundant mv instructions
RISC-V: mm: Document mmap changes
RISC-V: mm: Update pgtable comment documentation
RISC-V: mm: Add tests for RISC-V mm
RISC-V: mm: Restrict address space for sv39,sv48,sv57
riscv: enable DMA_BOUNCE_UNALIGNED_KMALLOC for !dma_coherent
riscv: allow kmalloc() caches aligned to the smallest value
riscv: support the elf-fdpic binfmt loader
binfmt_elf_fdpic: support 64-bit systems
riscv: Allow CONFIG_CFI_CLANG to be selected
riscv/purgatory: Disable CFI
riscv: Add CFI error handling
riscv: Add ftrace_stub_graph
riscv: Add types to indirectly called assembly functions
...
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We used to unconditionnally expose the cycle and instret csrs to
userspace, which gives rise to security concerns.
So now we only allow access to hw counters from userspace through the perf
framework which will handle context switches, per-task events...etc. A
sysctl allows to revert the behaviour to the legacy mode so that userspace
applications which are not ready for this change do not break.
But the default value is to allow userspace only through perf: this will
break userspace applications which rely on direct access to rdcycle.
This choice was made for security reasons [1][2]: most of the applications
which use rdcycle can instead use rdtime to count the elapsed time.
[1] https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/REWcwYnzsKE?pli=1
[2] https://www.youtube.com/watch?v=3-c4C_L2PRQ&ab_channel=IEEESymposiumonSecurityandPrivacy
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
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Provide all the necessary bits in the generic riscv pmu driver to be
able to mmap perf events in userspace: the heavy lifting lies in the
driver backend, namely the legacy and sbi implementations.
Note that arch_perf_update_userpage is almost a copy of arm64 code.
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
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Since commit 096b52fd2bb4 ("perf: RISC-V: throttle perf events") the
perf_sample_event_took() function was added to report time spent in
overflow interrupts. If the interrupt takes too long, the perf framework
will lower the sysctl_perf_event_sample_rate and max_samples_per_tick.
When hwc->interrupts is larger than max_samples_per_tick, the
hwc->interrupts will be set to MAX_INTERRUPTS, and events will be
throttled within the __perf_event_account_interrupt() function.
However, the RISC-V PMU driver doesn't call riscv_pmu_stop() to update the
PERF_HES_STOPPED flag after perf_event_overflow() in pmu_sbi_ovf_handler()
function to avoid throttling. When the perf framework unthrottled the event
in the timer interrupt handler, it triggers riscv_pmu_start() function
and causes a WARN_ON_ONCE() warning, as shown below:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 240 at drivers/perf/riscv_pmu.c:184 riscv_pmu_start+0x7c/0x8e
Modules linked in:
CPU: 0 PID: 240 Comm: ls Not tainted 6.4-rc4-g19d0788e9ef2 #1
Hardware name: SiFive (DT)
epc : riscv_pmu_start+0x7c/0x8e
ra : riscv_pmu_start+0x28/0x8e
epc : ffffffff80aef864 ra : ffffffff80aef810 sp : ffff8f80004db6f0
gp : ffffffff81c83750 tp : ffffaf80069f9bc0 t0 : ffff8f80004db6c0
t1 : 0000000000000000 t2 : 000000000000001f s0 : ffff8f80004db720
s1 : ffffaf8008ca1068 a0 : 0000ffffffffffff a1 : 0000000000000000
a2 : 0000000000000001 a3 : 0000000000000870 a4 : 0000000000000000
a5 : 0000000000000000 a6 : 0000000000000840 a7 : 0000000000000030
s2 : 0000000000000000 s3 : ffffaf8005165800 s4 : ffffaf800424da00
s5 : ffffffffffffffff s6 : ffffffff81cc7590 s7 : 0000000000000000
s8 : 0000000000000006 s9 : 0000000000000001 s10: ffffaf807efbc340
s11: ffffaf807efbbf00 t3 : ffffaf8006a16028 t4 : 00000000dbfbb796
t5 : 0000000700000000 t6 : ffffaf8005269870
status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
[<ffffffff80aef864>] riscv_pmu_start+0x7c/0x8e
[<ffffffff80185b56>] perf_adjust_freq_unthr_context+0x15e/0x174
[<ffffffff80188642>] perf_event_task_tick+0x88/0x9c
[<ffffffff800626a8>] scheduler_tick+0xfe/0x27c
[<ffffffff800b5640>] update_process_times+0x9a/0xba
[<ffffffff800c5bd4>] tick_sched_handle+0x32/0x66
[<ffffffff800c5e0c>] tick_sched_timer+0x64/0xb0
[<ffffffff800b5e50>] __hrtimer_run_queues+0x156/0x2f4
[<ffffffff800b6bdc>] hrtimer_interrupt+0xe2/0x1fe
[<ffffffff80acc9e8>] riscv_timer_interrupt+0x38/0x42
[<ffffffff80090a16>] handle_percpu_devid_irq+0x90/0x1d2
[<ffffffff8008a9f4>] generic_handle_domain_irq+0x28/0x36
After referring other PMU drivers like Arm, Loongarch, Csky, and Mips,
they don't call *_pmu_stop() to update with PERF_HES_STOPPED flag
after perf_event_overflow() function nor do they add PERF_HES_STOPPED
flag checking in *_pmu_start() which don't cause this warning.
Thus, it's recommended to remove this unnecessary check in
riscv_pmu_start() function to prevent this warning.
Signed-off-by: Eric Lin <eric.lin@sifive.com>
Link: https://lore.kernel.org/r/20230710154328.19574-1-eric.lin@sifive.com
Fixes: 096b52fd2bb4 ("perf: RISC-V: throttle perf events")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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A series of mostly-independent fixes and cleanups for the RISC-V PMU
drivers.
Link: https://lore.kernel.org/lkml/CAAhSdy23vE8+HxU5Jxy2rBMjy3rBTrJt_4sriuROac_sEESSVw@mail.gmail.com/T/#m9de15aef1b65ae6155fa33ea1239578ef463c2a2
* palmer/riscv-pmu:
RISC-V: Improve SBI definitions
RISC-V: Move counter info definition to sbi header file
RISC-V: Fix SBI PMU calls for RV32
RISC-V: Update user page mapping only once during start
RISC-V: Fix counter restart during overflow for RV32
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Currently, riscv_pmu_event_set_period updates the userpage mapping.
However, the caller of riscv_pmu_event_set_period should update
the userpage mapping because the counter can not be updated/started
from set_period function in counter overflow path.
Invoke the perf_event_update_userpage at the caller so that it
doesn't get invoked twice during counter start path.
Fixes: f5bfa23f576f ("RISC-V: Add a perf core library for pmu drivers")
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220711174632.4186047-3-atishp@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Currently, when the CPU is doing suspend to ram, we don't
save pmu counter register and its content will be lost.
To ensure perf profiling is not affected by suspend to ram,
this patch is based on arm_pmu CPU_PM notifier and implements riscv
pmu pm notifier. In the pm notifier, we stop the counter and update
the counter value before suspend and start the counter after resume.
Signed-off-by: Eric Lin <eric.lin@sifive.com>
Link: https://lore.kernel.org/r/20220705091920.27432-1-eric.lin@sifive.com
Signed-off-by: Will Deacon <will@kernel.org>
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RISC-V SBI specification added a PMU extension that allows to configure
start/stop any pmu counter. The RISC-V perf can use most of the generic
perf features except interrupt overflow and event filtering based on
privilege mode which will be added in future.
It also allows to monitor a handful of firmware counters that can provide
insights into firmware activity during a performance analysis.
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Implement a perf core library that can support all the essential perf
features in future. It can also accommodate any type of PMU implementation
in future. Currently, both SBI based perf driver and legacy driver
implemented uses the library. Most of the common perf functionalities
are kept in this core library wile PMU specific driver can implement PMU
specific features. For example, the SBI specific functionality will be
implemented in the SBI specific driver.
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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