From: Song Liu <songliubraving@fb.com>

Date: Thu, 11 Nov 2021 21:45:10 -0800

Subject: x86/perf: Fix snapshot_branch_stack warning in VM

Git-commit: f3fd84a3b7754b60df67ebfe64e1d90623895111

Patch-mainline: v5.16-rc2

References: git fixes

When running in VM intel_pmu_snapshot_branch_stack triggers WRMSR warning

like:

 [ ] unchecked MSR access error: WRMSR to 0x3f1 (tried to write 0x0000000000000000) at rIP: 0xffffffff81011a5b (intel_pmu_snapshot_branch_stack+0x3b/0xd0)

This can be triggered with BPF selftests:

  tools/testing/selftests/bpf/test_progs -t get_branch_snapshot

This warning is caused by __intel_pmu_pebs_disable_all() in the VM.

Since it is not necessary to disable PEBS for LBR, remove it from

intel_pmu_snapshot_branch_stack and intel_pmu_snapshot_arch_branch_stack.

Fixes: c22ac2a3d4bd ("perf: Enable branch record for software events")

Signed-off-by: Song Liu <songliubraving@fb.com>

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Tested-by: Like Xu <likexu@tencent.com>

Link: https://lore.kernel.org/r/20211112054510.2667030-1-songliubraving@fb.com

Signed-off-by: Tony Jones <tonyj@suse.de>

---

 arch/x86/events/intel/core.c | 2 --

 1 file changed, 2 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c

index 42cf01ecdd13..ec6444f2c9dc 100644

--- a/arch/x86/events/intel/core.c

+++ b/arch/x86/events/intel/core.c

@@ -2211,7 +2211,6 @@ intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int

 	/* must not have branches... */

 	local_irq_save(flags);

 	__intel_pmu_disable_all(false); /* we don't care about BTS */

-	__intel_pmu_pebs_disable_all();

 	__intel_pmu_lbr_disable();

 	/*            ... until here */

 	return __intel_pmu_snapshot_branch_stack(entries, cnt, flags);

@@ -2225,7 +2224,6 @@ intel_pmu_snapshot_arch_branch_stack(struct perf_branch_entry *entries, unsigned

 	/* must not have branches... */

 	local_irq_save(flags);

 	__intel_pmu_disable_all(false); /* we don't care about BTS */

-	__intel_pmu_pebs_disable_all();

 	__intel_pmu_arch_lbr_disable();

 	/*            ... until here */

 	return __intel_pmu_snapshot_branch_stack(entries, cnt, flags);