Patch "KVM: x86/pmu: Zero out PMU metadata on AMD if PMU is disabled" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    KVM: x86/pmu: Zero out PMU metadata on AMD if PMU is disabled

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-x86-pmu-zero-out-pmu-metadata-on-amd-if-pmu-is-d.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 6d2709c88a3a728025bd1be7a69873024c6790dc
Author: Sean Christopherson <seanjc@xxxxxxxxxx>
Date:   Thu Nov 9 18:28:48 2023 -0800

    KVM: x86/pmu: Zero out PMU metadata on AMD if PMU is disabled
    
    [ Upstream commit f933b88e20150f15787390e2a1754a7e412754ed ]
    
    Move the purging of common PMU metadata from intel_pmu_refresh() to
    kvm_pmu_refresh(), and invoke the vendor refresh() hook if and only if
    the VM is supposed to have a vPMU.
    
    KVM already denies access to the PMU based on kvm->arch.enable_pmu, as
    get_gp_pmc_amd() returns NULL for all PMCs in that case, i.e. KVM already
    violates AMD's architecture by not virtualizing a PMU (kernels have long
    since learned to not panic when the PMU is unavailable).  But configuring
    the PMU as if it were enabled causes unwanted side effects, e.g. calls to
    kvm_pmu_trigger_event() waste an absurd number of cycles due to the
    all_valid_pmc_idx bitmap being non-zero.
    
    Fixes: b1d66dad65dc ("KVM: x86/svm: Add module param to control PMU virtualization")
    Reported-by: Konstantin Khorenko <khorenko@xxxxxxxxxxxxx>
    Closes: https://lore.kernel.org/all/20231109180646.2963718-2-khorenko@xxxxxxxxxxxxx
    Link: https://lore.kernel.org/r/20231110022857.1273836-2-seanjc@xxxxxxxxxx
    Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
    Stable-dep-of: de120e1d692d ("KVM: x86/pmu: Set enable bits for GP counters in PERF_GLOBAL_CTRL at "RESET"")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 87cc6c8809ad8..38512954ec267 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -741,6 +741,8 @@ static void kvm_pmu_reset(struct kvm_vcpu *vcpu)
  */
 void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
 {
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
 	if (KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm))
 		return;
 
@@ -750,8 +752,22 @@ void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
 	 */
 	kvm_pmu_reset(vcpu);
 
-	bitmap_zero(vcpu_to_pmu(vcpu)->all_valid_pmc_idx, X86_PMC_IDX_MAX);
-	static_call(kvm_x86_pmu_refresh)(vcpu);
+	pmu->version = 0;
+	pmu->nr_arch_gp_counters = 0;
+	pmu->nr_arch_fixed_counters = 0;
+	pmu->counter_bitmask[KVM_PMC_GP] = 0;
+	pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
+	pmu->reserved_bits = 0xffffffff00200000ull;
+	pmu->raw_event_mask = X86_RAW_EVENT_MASK;
+	pmu->global_ctrl_mask = ~0ull;
+	pmu->global_status_mask = ~0ull;
+	pmu->fixed_ctr_ctrl_mask = ~0ull;
+	pmu->pebs_enable_mask = ~0ull;
+	pmu->pebs_data_cfg_mask = ~0ull;
+	bitmap_zero(pmu->all_valid_pmc_idx, X86_PMC_IDX_MAX);
+
+	if (vcpu->kvm->arch.enable_pmu)
+		static_call(kvm_x86_pmu_refresh)(vcpu);
 }
 
 void kvm_pmu_init(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 315c7c2ba89b1..600a021ae958b 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -491,19 +491,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	u64 counter_mask;
 	int i;
 
-	pmu->nr_arch_gp_counters = 0;
-	pmu->nr_arch_fixed_counters = 0;
-	pmu->counter_bitmask[KVM_PMC_GP] = 0;
-	pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
-	pmu->version = 0;
-	pmu->reserved_bits = 0xffffffff00200000ull;
-	pmu->raw_event_mask = X86_RAW_EVENT_MASK;
-	pmu->global_ctrl_mask = ~0ull;
-	pmu->global_status_mask = ~0ull;
-	pmu->fixed_ctr_ctrl_mask = ~0ull;
-	pmu->pebs_enable_mask = ~0ull;
-	pmu->pebs_data_cfg_mask = ~0ull;
-
 	memset(&lbr_desc->records, 0, sizeof(lbr_desc->records));
 
 	/*
@@ -515,8 +502,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		return;
 
 	entry = kvm_find_cpuid_entry(vcpu, 0xa);
-	if (!entry || !vcpu->kvm->arch.enable_pmu)
+	if (!entry)
 		return;
+
 	eax.full = entry->eax;
 	edx.full = entry->edx;