From cf52de619c67bd1f6b1cf2751c3827815f74a5a5 Mon Sep 17 00:00:00 2001
From: Like Xu <likexu@tencent.com>
Date: Wed, 31 Aug 2022 16:53:24 +0800
Subject: [PATCH] KVM: x86/pmu: Avoid using PEBS perf_events for normal
counters
The check logic in the pmc_resume_counter() to determine whether
a perf_event is reusable is partial and flawed, especially when it
comes to a pseudocode sequence (contrived, but valid) like:
- enabling a counter and its PEBS bit
- enable global_ctrl
- run workload
- disable only the PEBS bit, leaving the global_ctrl bit enabled
In this corner case, a perf_event created for PEBS can be reused by
a normal counter before it has been released and recreated, and when this
normal counter overflows, it triggers a PEBS interrupt (precise_ip != 0).
To address this issue, reprogram all affected counters when PEBS_ENABLE
change and reuse a counter if and only if PEBS exactly matches precise.
Fixes: 79f3e3b58386 ("KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter")
Signed-off-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20220831085328.45489-4-likexu@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/pmu.c | 4 ++--
arch/x86/kvm/vmx/pmu_intel.c | 2 ++
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 390d697efde14..d9b9a0f0db17c 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -237,8 +237,8 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc)
get_sample_period(pmc, pmc->counter)))
return false;
- if (!test_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->pebs_enable) &&
- pmc->perf_event->attr.precise_ip)
+ if (test_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->pebs_enable) !=
+ (!!pmc->perf_event->attr.precise_ip))
return false;
/* reuse perf_event to serve as pmc_reprogram_counter() does*/
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 5592b1259e1bb..25b70a85bef54 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -431,7 +431,9 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (pmu->pebs_enable == data)
return 0;
if (!(data & pmu->pebs_enable_mask)) {
+ diff = pmu->pebs_enable ^ data;
pmu->pebs_enable = data;
+ reprogram_counters(pmu, diff);
return 0;
}
break;