The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
b333b8ebb85d ("KVM: VMX: Ignore guest CPUID for host userspace writes to DEBUGCTL") 18e897d213cb ("KVM: VMX: Fold vmx_supported_debugctl() into vcpu_supported_debugctl()") 2f4073e08f4c ("KVM: VMX: Enable Notify VM exit") 938c8745bcf2 ("KVM: x86: Introduce "struct kvm_caps" to track misc caps/settings") ed2351174e38 ("KVM: x86: Extend KVM_{G,S}ET_VCPU_EVENTS to support pending triple fault") 35875316384b ("KVM: x86: Allow userspace to set maximum VCPU id for VM") e9bf3acb23f0 ("KVM: s390: Add KVM_CAP_S390_PROTECTED_DUMP") 8aba09588d2a ("KVM: s390: Add CPU dump functionality") 0460eb35b443 ("KVM: s390: Add configuration dump functionality") 35d02493dba1 ("KVM: s390: pv: Add query interface") 47e8eec83262 ("Merge tag 'kvmarm-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b333b8ebb85d62469f32b52fa03fd7d1522afc03 Mon Sep 17 00:00:00 2001 From: Sean Christopherson seanjc@google.com Date: Thu, 6 Oct 2022 00:03:10 +0000 Subject: [PATCH] KVM: VMX: Ignore guest CPUID for host userspace writes to DEBUGCTL
Ignore guest CPUID for host userspace writes to the DEBUGCTL MSR, KVM's ABI is that setting CPUID vs. state can be done in any order, i.e. KVM allows userspace to stuff MSRs prior to setting the guest's CPUID that makes the new MSR "legal".
Keep the vmx_get_perf_capabilities() check for guest writes, even though it's technically unnecessary since the vCPU's PERF_CAPABILITIES is consulted when refreshing LBR support. A future patch will clean up vmx_get_perf_capabilities() to avoid the RDMSR on every call, at which point the paranoia will incur no meaningful overhead.
Note, prior to vmx_get_perf_capabilities() checking that the host fully supports LBRs via x86_perf_get_lbr(), KVM effectively relied on intel_pmu_lbr_is_enabled() to guard against host userspace enabling LBRs on platforms without full support.
Fixes: c646236344e9 ("KVM: vmx/pmu: Add PMU_CAP_LBR_FMT check when guest LBR is enabled") Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20221006000314.73240-5-seanjc@google.com Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 981b38355066..63247c57c72c 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -2021,16 +2021,16 @@ static u64 nested_vmx_truncate_sysenter_addr(struct kvm_vcpu *vcpu, return (unsigned long)data; }
-static u64 vcpu_supported_debugctl(struct kvm_vcpu *vcpu) +static u64 vmx_get_supported_debugctl(struct kvm_vcpu *vcpu, bool host_initiated) { u64 debugctl = 0;
if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT) && - guest_cpuid_has(vcpu, X86_FEATURE_BUS_LOCK_DETECT)) + (host_initiated || guest_cpuid_has(vcpu, X86_FEATURE_BUS_LOCK_DETECT))) debugctl |= DEBUGCTLMSR_BUS_LOCK_DETECT;
if ((vmx_get_perf_capabilities() & PMU_CAP_LBR_FMT) && - intel_pmu_lbr_is_enabled(vcpu)) + (host_initiated || intel_pmu_lbr_is_enabled(vcpu))) debugctl |= DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI;
return debugctl; @@ -2105,7 +2105,9 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) vmcs_writel(GUEST_SYSENTER_ESP, data); break; case MSR_IA32_DEBUGCTLMSR: { - u64 invalid = data & ~vcpu_supported_debugctl(vcpu); + u64 invalid; + + invalid = data & ~vmx_get_supported_debugctl(vcpu, msr_info->host_initiated); if (invalid & (DEBUGCTLMSR_BTF|DEBUGCTLMSR_LBR)) { if (report_ignored_msrs) vcpu_unimpl(vcpu, "%s: BTF|LBR in IA32_DEBUGCTLMSR 0x%llx, nop\n",