KVM: x86/pmu: Disable counters based on Host-Only/Guest-Only bits in SVM

Introduce an optional per-vendor PMU callback for checking if a counter
is disabled in the current mode, and register a callback on AMD to
disable a counter based on the vCPU's setting of Host-Only or Guest-Only
EVENT_SELECT bits with the mediated PMU.

If EFER.SVME is set, all events are counted if both bits are set or
cleared. If only one bit is set, the counter is disabled if the vCPU
context does not match the set bit.

If EFER.SVME is cleared, the counter is disabled if any of the bits is
set, otherwise all events are counted. Note that a Linux guest correctly
handles this and clears Host-Only when EFER.SVME is cleared, see commit
1018faa6cf23 ("perf/x86/kvm: Fix Host-Only/Guest-Only counting with SVM
disabled").

The callback is made from pmc_is_locally_enabled(), which is used for
the mediated PMU when updating eventsel_hw in
kvm_mediated_pmu_refresh_eventsel_hw(), as well as when checking what
PMCs count instructions/branches for emulation in
kvm_pmu_recalc_pmc_emulation().

Host-Only and Guest-Only bits are currently reserved, so this change is
a noop, but the bits will be allowed with mediated PMU in a following
change when fully supported.

Originally-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260527234711.4175166-11-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/include/asm/kvm-x86-pmu-ops.h b/arch/x86/include/asm/kvm-x86-pmu-ops.h
index 0616243c84cf9ff98815f3d213383a3c8a0370f0..4a223c2793e3fdaaf9da27d86d2cece19ceda2d3 100644 (file)
--- a/arch/x86/include/asm/kvm-x86-pmu-ops.h
+++ b/arch/x86/include/asm/kvm-x86-pmu-ops.h
@@ -24,6 +24,7 @@ KVM_X86_PMU_OP(init)
 KVM_X86_PMU_OP_OPTIONAL(reset)
 KVM_X86_PMU_OP_OPTIONAL(deliver_pmi)
 KVM_X86_PMU_OP_OPTIONAL(cleanup)
+KVM_X86_PMU_OP_OPTIONAL_RET0(pmc_is_disabled_in_current_mode)
 
 KVM_X86_PMU_OP_OPTIONAL(write_global_ctrl)
 KVM_X86_PMU_OP(mediated_load)

diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 752cb319d5eaba2c60fbc846bf432c2e673718a7..1eb13673e889f95864444d82ae31b1df4dd2cce2 100644 (file)
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -60,6 +60,8 @@
 #define AMD64_EVENTSEL_INT_CORE_ENABLE                 (1ULL << 36)
 #define AMD64_EVENTSEL_GUESTONLY                       (1ULL << 40)
 #define AMD64_EVENTSEL_HOSTONLY                                (1ULL << 41)
+#define AMD64_EVENTSEL_HOST_GUEST_MASK                 \
+       (AMD64_EVENTSEL_HOSTONLY | AMD64_EVENTSEL_GUESTONLY)
 
 #define AMD64_EVENTSEL_INT_CORE_SEL_SHIFT              37
 #define AMD64_EVENTSEL_INT_CORE_SEL_MASK               \

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 9b7e39610be22d2f151a6cc7e5fd27573f21e455..8159b07e9bc2078991d9f9dc9cf51e7627bdebed 100644 (file)
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -100,6 +100,7 @@ static struct kvm_pmu_ops kvm_pmu_ops __read_mostly;
 #define KVM_X86_PMU_OP_OPTIONAL KVM_X86_PMU_OP
 #define KVM_X86_PMU_OP_OPTIONAL_RET0 KVM_X86_PMU_OP
 #include <asm/kvm-x86-pmu-ops.h>
+EXPORT_STATIC_CALL_GPL(kvm_x86_pmu_pmc_is_disabled_in_current_mode);
 
 void kvm_pmu_ops_update(const struct kvm_pmu_ops *pmu_ops)
 {

diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index a062f0bc3dbb1d188cb8dcf992eb6014c4186910..71c7853e8ae5fd4138833d7e61a7f79ee046e642 100644 (file)
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -36,6 +36,7 @@ struct kvm_pmu_ops {
        void (*reset)(struct kvm_vcpu *vcpu);
        void (*deliver_pmi)(struct kvm_vcpu *vcpu);
        void (*cleanup)(struct kvm_vcpu *vcpu);
+       bool (*pmc_is_disabled_in_current_mode)(struct kvm_pmc *pmc);
 
        bool (*is_mediated_pmu_supported)(struct x86_pmu_capability *host_pmu);
        void (*mediated_load)(struct kvm_vcpu *vcpu);
@@ -201,7 +202,8 @@ static inline bool pmc_is_locally_enabled(struct kvm_pmc *pmc)
                                        pmc->idx - KVM_FIXED_PMC_BASE_IDX) &
                                        (INTEL_FIXED_0_KERNEL | INTEL_FIXED_0_USER);
 
-       return pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE;
+       return (pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE) &&
+              !kvm_pmu_call(pmc_is_disabled_in_current_mode)(pmc);
 }
 
 extern struct x86_pmu_capability kvm_pmu_cap;

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 7aa298eeb0721b7bb349c84ce0d8b6bed454fbd7..41ee6532290e9299253a5bbb2058dc0559a6c20f 100644 (file)
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -260,6 +260,37 @@ static void amd_mediated_pmu_put(struct kvm_vcpu *vcpu)
                wrmsrq(MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR, pmu->global_status);
 }
 
+static bool amd_pmc_is_disabled_in_current_mode(struct kvm_pmc *pmc)
+{
+       struct kvm_vcpu *vcpu = pmc->vcpu;
+       u64 host_guest_bits;
+
+       if (!kvm_vcpu_has_mediated_pmu(vcpu))
+               return false;
+
+       /* Common code is supposed to check the common enable bit */
+       if (WARN_ON_ONCE(!(pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE)))
+               return false;
+
+       /* If both bits are cleared, the counter is always enabled */
+       host_guest_bits = pmc->eventsel & AMD64_EVENTSEL_HOST_GUEST_MASK;
+       if (!host_guest_bits)
+               return false;
+
+       /* If EFER.SVME=0 and either bit is set, the counter is disabled */
+       if (!(vcpu->arch.efer & EFER_SVME))
+               return true;
+
+       /*
+        * If EFER.SVME=1, the counter is disabled iff only one of the bits is
+        * set AND the set bit doesn't match the vCPU mode.
+        */
+       if (host_guest_bits == AMD64_EVENTSEL_HOST_GUEST_MASK)
+               return false;
+
+       return !!(host_guest_bits & AMD64_EVENTSEL_GUESTONLY) != is_guest_mode(vcpu);
+}
+
 struct kvm_pmu_ops amd_pmu_ops __initdata = {
        .rdpmc_ecx_to_pmc = amd_rdpmc_ecx_to_pmc,
        .msr_idx_to_pmc = amd_msr_idx_to_pmc,
@@ -269,6 +300,7 @@ struct kvm_pmu_ops amd_pmu_ops __initdata = {
        .set_msr = amd_pmu_set_msr,
        .refresh = amd_pmu_refresh,
        .init = amd_pmu_init,
+       .pmc_is_disabled_in_current_mode = amd_pmc_is_disabled_in_current_mode,
 
        .is_mediated_pmu_supported = amd_pmu_is_mediated_pmu_supported,
        .mediated_load = amd_mediated_pmu_load,