perf/x86/core: Completely disable guest PEBS via guest's global_ctrl
authorLike Xu <likexu@tencent.com>
Wed, 31 Aug 2022 03:35:24 +0000 (11:35 +0800)
committerPeter Zijlstra <peterz@infradead.org>
Thu, 1 Sep 2022 09:19:42 +0000 (11:19 +0200)
commitf2aeea57504cbbc58da3c59b939fc16150087648
treec550decf5a6ea2e94397a4ba5e4d85ec7f40ab6f
parent24919fdea6f8b31d7cdf32ac291bc5dd0b023878
perf/x86/core: Completely disable guest PEBS via guest's global_ctrl

When a guest PEBS counter is cross-mapped by a host counter, software
will remove the corresponding bit in the arr[global_ctrl].guest and
expect hardware to perform a change of state "from enable to disable"
via the msr_slot[] switch during the vmx transaction.

The real world is that if user adjust the counter overflow value small
enough, it still opens a tiny race window for the previously PEBS-enabled
counter to write cross-mapped PEBS records into the guest's PEBS buffer,
when arr[global_ctrl].guest has been prioritised (switch_msr_special stuff)
to switch into the enabled state, while the arr[pebs_enable].guest has not.

Close this window by clearing invalid bits in the arr[global_ctrl].guest.

Fixes: 854250329c02 ("KVM: x86/pmu: Disable guest PEBS temporarily in two rare situations")
Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220831033524.58561-1-likexu@tencent.com
arch/x86/events/intel/core.c