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authorJiri Olsa <jolsa@kernel.org>2020-04-07 16:14:27 +0200
committerIngo Molnar <mingo@kernel.org>2020-04-08 11:33:46 +0200
commitd3296fb372bf7497b0e5d0478c4e7a677ec6f6e9 (patch)
tree7cecee8c57730cc38b87cd610595721a955ab666
parent2b3b76b5ec67568da4bb475d3ce8a92ef494b5de (diff)
downloadlinux-stericsson-d3296fb372bf7497b0e5d0478c4e7a677ec6f6e9.tar.gz
perf/core: Disable page faults when getting phys address
We hit following warning when running tests on kernel compiled with CONFIG_DEBUG_ATOMIC_SLEEP=y: WARNING: CPU: 19 PID: 4472 at mm/gup.c:2381 __get_user_pages_fast+0x1a4/0x200 CPU: 19 PID: 4472 Comm: dummy Not tainted 5.6.0-rc6+ #3 RIP: 0010:__get_user_pages_fast+0x1a4/0x200 ... Call Trace: perf_prepare_sample+0xff1/0x1d90 perf_event_output_forward+0xe8/0x210 __perf_event_overflow+0x11a/0x310 __intel_pmu_pebs_event+0x657/0x850 intel_pmu_drain_pebs_nhm+0x7de/0x11d0 handle_pmi_common+0x1b2/0x650 intel_pmu_handle_irq+0x17b/0x370 perf_event_nmi_handler+0x40/0x60 nmi_handle+0x192/0x590 default_do_nmi+0x6d/0x150 do_nmi+0x2f9/0x3c0 nmi+0x8e/0xd7 While __get_user_pages_fast() is IRQ-safe, it calls access_ok(), which warns on: WARN_ON_ONCE(!in_task() && !pagefault_disabled()) Peter suggested disabling page faults around __get_user_pages_fast(), which gets rid of the warning in access_ok() call. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20200407141427.3184722-1-jolsa@kernel.org
-rw-r--r--kernel/events/core.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 26de0a5ee887..bc9b98a9af9a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6934,9 +6934,12 @@ static u64 perf_virt_to_phys(u64 virt)
* Try IRQ-safe __get_user_pages_fast first.
* If failed, leave phys_addr as 0.
*/
- if ((current->mm != NULL) &&
- (__get_user_pages_fast(virt, 1, 0, &p) == 1))
- phys_addr = page_to_phys(p) + virt % PAGE_SIZE;
+ if (current->mm != NULL) {
+ pagefault_disable();
+ if (__get_user_pages_fast(virt, 1, 0, &p) == 1)
+ phys_addr = page_to_phys(p) + virt % PAGE_SIZE;
+ pagefault_enable();
+ }
if (p)
put_page(p);