From c435978e4ffe87c6baee1290118039187eafc698 Mon Sep 17 00:00:00 2001 From: dongsheng Date: Fri, 19 Sep 2025 14:46:48 -0700 Subject: KVM: selftests: Handle Intel Atom errata that leads to PMU event overcount Add a PMU errata framework and use it to relax precise event counts on Atom platforms that overcount "Instruction Retired" and "Branch Instruction Retired" events, as the overcount issues on VM-Exit/VM-Entry are impossible to prevent from userspace, e.g. the test can't prevent host IRQs. Setup errata during early initialization and automatically sync the mask to VMs so that tests can check for errata without having to manually manage host=>guest variables. For Intel Atom CPUs, the PMU events "Instruction Retired" or "Branch Instruction Retired" may be overcounted for some certain instructions, like FAR CALL/JMP, RETF, IRET, VMENTRY/VMEXIT/VMPTRLD and complex SGX/SMX/CSTATE instructions/flows. The detailed information can be found in the errata (section SRF7): https://edc.intel.com/content/www/us/en/design/products-and-solutions/processors-and-chipsets/sierra-forest/xeon-6700-series-processor-with-e-cores-specification-update/errata-details/ For the Atom platforms before Sierra Forest (including Sierra Forest), Both 2 events "Instruction Retired" and "Branch Instruction Retired" would be overcounted on these certain instructions, but for Clearwater Forest only "Instruction Retired" event is overcounted on these instructions. Signed-off-by: dongsheng Co-developed-by: Dapeng Mi Signed-off-by: Dapeng Mi Tested-by: Yi Lai Co-developed-by: Sean Christopherson Reviewed-by: Dapeng Mi Tested-by: Dapeng Mi Link: https://lore.kernel.org/r/20250919214648.1585683-6-seanjc@google.com Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/lib/x86/processor.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'tools/testing/selftests/kvm/lib/x86/processor.c') diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c index 3b63c99f7b96..4402d2e1ea69 100644 --- a/tools/testing/selftests/kvm/lib/x86/processor.c +++ b/tools/testing/selftests/kvm/lib/x86/processor.c @@ -6,6 +6,7 @@ #include "linux/bitmap.h" #include "test_util.h" #include "kvm_util.h" +#include "pmu.h" #include "processor.h" #include "sev.h" @@ -638,6 +639,7 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm) sync_global_to_guest(vm, host_cpu_is_intel); sync_global_to_guest(vm, host_cpu_is_amd); sync_global_to_guest(vm, is_forced_emulation_enabled); + sync_global_to_guest(vm, pmu_errata_mask); if (is_sev_vm(vm)) { struct kvm_sev_init init = { 0 }; @@ -1269,6 +1271,8 @@ void kvm_selftest_arch_init(void) host_cpu_is_intel = this_cpu_is_intel(); host_cpu_is_amd = this_cpu_is_amd(); is_forced_emulation_enabled = kvm_is_forced_emulation_enabled(); + + kvm_init_pmu_errata(); } bool sys_clocksource_is_based_on_tsc(void) -- cgit v1.2.3