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authorMarc Zyngier <maz@kernel.org>2023-08-20 12:01:08 +0300
committerMarc Zyngier <maz@kernel.org>2023-08-22 15:35:51 +0300
commitb1f778a223a2a8ad6262e5233cfc3483bcf6e213 (patch)
tree856ac471c560ce076e04499093e3e034a108bf02 /arch/arm
parent64b81000b60b70f10a5834023fe100902d9f7a57 (diff)
downloadlinux-b1f778a223a2a8ad6262e5233cfc3483bcf6e213.tar.xz
KVM: arm64: pmu: Resync EL0 state on counter rotation
Huang Shijie reports that, when profiling a guest from the host with a number of events that exceeds the number of available counters, the reported counts are wildly inaccurate. Without the counter oversubscription, the reported counts are correct. Their investigation indicates that upon counter rotation (which takes place on the back of a timer interrupt), we fail to re-apply the guest EL0 enabling, leading to the counting of host events instead of guest events. In order to solve this, add yet another hook between the host PMU driver and KVM, re-applying the guest EL0 configuration if the right conditions apply (the host is VHE, we are in interrupt context, and we interrupted a running vcpu). This triggers a new vcpu request which will apply the correct configuration on guest reentry. With this, we have the correct counts, even when the counters are oversubscribed. Reported-by: Huang Shijie <shijie@os.amperecomputing.com> Suggested-by: Oliver Upton <oliver.upton@linux.dev> Tested_by: Huang Shijie <shijie@os.amperecomputing.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Cc: Leo Yan <leo.yan@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20230809013953.7692-1-shijie@os.amperecomputing.com Acked-by: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20230820090108.177817-1-maz@kernel.org
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/include/asm/arm_pmuv3.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/arm/include/asm/arm_pmuv3.h b/arch/arm/include/asm/arm_pmuv3.h
index f3cd04ff022d..72529f5e2bed 100644
--- a/arch/arm/include/asm/arm_pmuv3.h
+++ b/arch/arm/include/asm/arm_pmuv3.h
@@ -227,6 +227,8 @@ static inline bool kvm_set_pmuserenr(u64 val)
return false;
}
+static inline void kvm_vcpu_pmu_resync_el0(void) {}
+
/* PMU Version in DFR Register */
#define ARMV8_PMU_DFR_VER_NI 0
#define ARMV8_PMU_DFR_VER_V3P4 0x5