On Tue, May 10, 2022 at 4:38 AM Greg KH gregkh@linuxfoundation.org wrote:
On Tue, May 10, 2022 at 01:37:08PM +0200, Greg KH wrote:
On Mon, May 09, 2022 at 01:41:20PM +0200, Paolo Bonzini wrote:
On 5/8/22 18:54, Kyle Huey wrote:
From: Kyle Huey me@kylehuey.com
commit 5eb849322d7f7ae9d5c587c7bc3b4f7c6872cd2f upstream
Zen renumbered some of the performance counters that correspond to the well known events in perf_hw_id. This code in KVM was never updated for that, so guest that attempt to use counters on Zen that correspond to the pre-Zen perf_hw_id values will silently receive the wrong values.
This has been observed in the wild with rr[0] when running in Zen 3 guests. rr uses the retired conditional branch counter 00d1 which is incorrectly recognized by KVM as PERF_COUNT_HW_STALLED_CYCLES_BACKEND.
Signed-off-by: Kyle Huey me@kylehuey.com Message-Id: 20220503050136.86298-1-khuey@kylehuey.com Cc: stable@vger.kernel.org [Check guest family, not host. - Paolo] Signed-off-by: Paolo Bonzini pbonzini@redhat.com [Backport to 5.4: adjusted context] Signed-off-by: Kyle Huey me@kylehuey.com
arch/x86/kvm/pmu_amd.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/pmu_amd.c b/arch/x86/kvm/pmu_amd.c index 6bc656abbe66..3ccfd1abcbad 100644 --- a/arch/x86/kvm/pmu_amd.c +++ b/arch/x86/kvm/pmu_amd.c @@ -44,6 +44,22 @@ static struct kvm_event_hw_type_mapping amd_event_mapping[] = { [7] = { 0xd1, 0x00, PERF_COUNT_HW_STALLED_CYCLES_BACKEND }, }; +/* duplicated from amd_f17h_perfmon_event_map. */ +static struct kvm_event_hw_type_mapping amd_f17h_event_mapping[] = {
- [0] = { 0x76, 0x00, PERF_COUNT_HW_CPU_CYCLES },
- [1] = { 0xc0, 0x00, PERF_COUNT_HW_INSTRUCTIONS },
- [2] = { 0x60, 0xff, PERF_COUNT_HW_CACHE_REFERENCES },
- [3] = { 0x64, 0x09, PERF_COUNT_HW_CACHE_MISSES },
- [4] = { 0xc2, 0x00, PERF_COUNT_HW_BRANCH_INSTRUCTIONS },
- [5] = { 0xc3, 0x00, PERF_COUNT_HW_BRANCH_MISSES },
- [6] = { 0x87, 0x02, PERF_COUNT_HW_STALLED_CYCLES_FRONTEND },
- [7] = { 0x87, 0x01, PERF_COUNT_HW_STALLED_CYCLES_BACKEND },
+};
+/* amd_pmc_perf_hw_id depends on these being the same size */ +static_assert(ARRAY_SIZE(amd_event_mapping) ==
ARRAY_SIZE(amd_f17h_event_mapping));- static unsigned int get_msr_base(struct kvm_pmu *pmu, enum pmu_type type) { struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu);
@@ -130,17 +146,23 @@ static unsigned amd_find_arch_event(struct kvm_pmu *pmu, u8 event_select, u8 unit_mask) {
- struct kvm_event_hw_type_mapping *event_mapping; int i;
- if (guest_cpuid_family(pmc->vcpu) >= 0x17)
event_mapping = amd_f17h_event_mapping;- else
event_mapping = amd_event_mapping;for (i = 0; i < ARRAY_SIZE(amd_event_mapping); i++)
if (amd_event_mapping[i].eventsel == event_select&& amd_event_mapping[i].unit_mask == unit_mask)
if (event_mapping[i].eventsel == event_select&& event_mapping[i].unit_mask == unit_mask) break; if (i == ARRAY_SIZE(amd_event_mapping)) return PERF_COUNT_HW_MAX;
- return amd_event_mapping[i].event_type;
- return event_mapping[i].event_type; } /* return PERF_COUNT_HW_MAX as AMD doesn't have fixed events */
Acked-by: Paolo Bonzini pbonzini@redhat.com
Thanks,
Paolo
Wait, how was this tested?
It breaks the build:
arch/x86/kvm/pmu_amd.c: In function ‘amd_find_arch_event’: arch/x86/kvm/pmu_amd.c:152:32: error: ‘pmc’ undeclared (first use in this function); did you mean ‘pmu’? 152 | if (guest_cpuid_family(pmc->vcpu) >= 0x17) | ^~~ | pmu
I'll do the obvious fixup, but this is odd. Always at least test-build your changes...
Hm, no, I don't know what the correct fix is here. I'll wait for a fixed up (and tested) patch to be resubmited please.
thanks,
greg k-h
Sorry, I tested an earlier version without the guest_cpuid_family fix that Paolo made when he committed my patch, and of course that's the hang up here. I'll get this fixed up for you.
- Kyle