| From 7a29b546168ea7252a909633d7860beb1599191b Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Thu, 14 Aug 2025 17:11:52 -0700 |
| Subject: KVM: x86/pmu: Gate all "unimplemented MSR" prints on |
| report_ignored_msrs |
| |
| From: Sean Christopherson <seanjc@google.com> |
| |
| [ Upstream commit e76ae52747a82a548742107b4100e90da41a624d ] |
| |
| Add helpers to print unimplemented MSR accesses and condition all such |
| prints on report_ignored_msrs, i.e. honor userspace's request to not |
| print unimplemented MSRs. Even though vcpu_unimpl() is ratelimited, |
| printing can still be problematic, e.g. if a print gets stalled when host |
| userspace is writing MSRs during live migration, an effective stall can |
| result in very noticeable disruption in the guest. |
| |
| E.g. the profile below was taken while calling KVM_SET_MSRS on the PMU |
| counters while the PMU was disabled in KVM. |
| |
| - 99.75% 0.00% [.] __ioctl |
| - __ioctl |
| - 99.74% entry_SYSCALL_64_after_hwframe |
| do_syscall_64 |
| sys_ioctl |
| - do_vfs_ioctl |
| - 92.48% kvm_vcpu_ioctl |
| - kvm_arch_vcpu_ioctl |
| - 85.12% kvm_set_msr_ignored_check |
| svm_set_msr |
| kvm_set_msr_common |
| printk |
| vprintk_func |
| vprintk_default |
| vprintk_emit |
| console_unlock |
| call_console_drivers |
| univ8250_console_write |
| serial8250_console_write |
| uart_console_write |
| |
| Reported-by: Aaron Lewis <aaronlewis@google.com> |
| Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> |
| Link: https://lore.kernel.org/r/20230124234905.3774678-3-seanjc@google.com |
| Stable-dep-of: 7d0cce6cbe71 ("KVM: VMX: Wrap all accesses to IA32_DEBUGCTL with getter/setter APIs") |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| Signed-off-by: Sean Christopherson <seanjc@google.com> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/x86/kvm/hyperv.c | 10 ++++------ |
| arch/x86/kvm/svm/svm.c | 5 ++--- |
| arch/x86/kvm/vmx/vmx.c | 4 +--- |
| arch/x86/kvm/x86.c | 18 +++++------------- |
| arch/x86/kvm/x86.h | 12 ++++++++++++ |
| 5 files changed, 24 insertions(+), 25 deletions(-) |
| |
| diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c |
| index 28555bbd52e8..cb0a531e13c5 100644 |
| --- a/arch/x86/kvm/hyperv.c |
| +++ b/arch/x86/kvm/hyperv.c |
| @@ -1406,8 +1406,7 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data, |
| case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER: |
| return syndbg_set_msr(vcpu, msr, data, host); |
| default: |
| - vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n", |
| - msr, data); |
| + kvm_pr_unimpl_wrmsr(vcpu, msr, data); |
| return 1; |
| } |
| return 0; |
| @@ -1528,8 +1527,7 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host) |
| return 1; |
| break; |
| default: |
| - vcpu_unimpl(vcpu, "Hyper-V unhandled wrmsr: 0x%x data 0x%llx\n", |
| - msr, data); |
| + kvm_pr_unimpl_wrmsr(vcpu, msr, data); |
| return 1; |
| } |
| |
| @@ -1581,7 +1579,7 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, |
| case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER: |
| return syndbg_get_msr(vcpu, msr, pdata, host); |
| default: |
| - vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr); |
| + kvm_pr_unimpl_rdmsr(vcpu, msr); |
| return 1; |
| } |
| |
| @@ -1646,7 +1644,7 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, |
| data = APIC_BUS_FREQUENCY; |
| break; |
| default: |
| - vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr); |
| + kvm_pr_unimpl_rdmsr(vcpu, msr); |
| return 1; |
| } |
| *pdata = data; |
| diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c |
| index b922f31d1415..2c0f9c7d1242 100644 |
| --- a/arch/x86/kvm/svm/svm.c |
| +++ b/arch/x86/kvm/svm/svm.c |
| @@ -3035,8 +3035,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) |
| break; |
| case MSR_IA32_DEBUGCTLMSR: |
| if (!lbrv) { |
| - vcpu_unimpl(vcpu, "%s: MSR_IA32_DEBUGCTL 0x%llx, nop\n", |
| - __func__, data); |
| + kvm_pr_unimpl_wrmsr(vcpu, ecx, data); |
| break; |
| } |
| |
| @@ -3077,7 +3076,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) |
| case MSR_VM_CR: |
| return svm_set_vm_cr(vcpu, data); |
| case MSR_VM_IGNNE: |
| - vcpu_unimpl(vcpu, "unimplemented wrmsr: 0x%x data 0x%llx\n", ecx, data); |
| + kvm_pr_unimpl_wrmsr(vcpu, ecx, data); |
| break; |
| case MSR_AMD64_DE_CFG: { |
| struct kvm_msr_entry msr_entry; |
| diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c |
| index c24da2cff208..390af16d9a67 100644 |
| --- a/arch/x86/kvm/vmx/vmx.c |
| +++ b/arch/x86/kvm/vmx/vmx.c |
| @@ -2140,9 +2140,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) |
| |
| 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", |
| - __func__, data); |
| + kvm_pr_unimpl_wrmsr(vcpu, msr_index, data); |
| data &= ~(DEBUGCTLMSR_BTF|DEBUGCTLMSR_LBR); |
| invalid &= ~(DEBUGCTLMSR_BTF|DEBUGCTLMSR_LBR); |
| } |
| diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c |
| index b0ae61ba9b99..d224180c56f5 100644 |
| --- a/arch/x86/kvm/x86.c |
| +++ b/arch/x86/kvm/x86.c |
| @@ -3573,7 +3573,6 @@ static void record_steal_time(struct kvm_vcpu *vcpu) |
| |
| int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) |
| { |
| - bool pr = false; |
| u32 msr = msr_info->index; |
| u64 data = msr_info->data; |
| |
| @@ -3625,15 +3624,13 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) |
| if (data == BIT_ULL(18)) { |
| vcpu->arch.msr_hwcr = data; |
| } else if (data != 0) { |
| - vcpu_unimpl(vcpu, "unimplemented HWCR wrmsr: 0x%llx\n", |
| - data); |
| + kvm_pr_unimpl_wrmsr(vcpu, msr, data); |
| return 1; |
| } |
| break; |
| case MSR_FAM10H_MMIO_CONF_BASE: |
| if (data != 0) { |
| - vcpu_unimpl(vcpu, "unimplemented MMIO_CONF_BASE wrmsr: " |
| - "0x%llx\n", data); |
| + kvm_pr_unimpl_wrmsr(vcpu, msr, data); |
| return 1; |
| } |
| break; |
| @@ -3813,16 +3810,13 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) |
| |
| case MSR_K7_PERFCTR0 ... MSR_K7_PERFCTR3: |
| case MSR_P6_PERFCTR0 ... MSR_P6_PERFCTR1: |
| - pr = true; |
| - fallthrough; |
| case MSR_K7_EVNTSEL0 ... MSR_K7_EVNTSEL3: |
| case MSR_P6_EVNTSEL0 ... MSR_P6_EVNTSEL1: |
| if (kvm_pmu_is_valid_msr(vcpu, msr)) |
| return kvm_pmu_set_msr(vcpu, msr_info); |
| |
| - if (pr || data != 0) |
| - vcpu_unimpl(vcpu, "disabled perfctr wrmsr: " |
| - "0x%x data 0x%llx\n", msr, data); |
| + if (data) |
| + kvm_pr_unimpl_wrmsr(vcpu, msr, data); |
| break; |
| case MSR_K7_CLK_CTL: |
| /* |
| @@ -3849,9 +3843,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) |
| /* Drop writes to this legacy MSR -- see rdmsr |
| * counterpart for further detail. |
| */ |
| - if (report_ignored_msrs) |
| - vcpu_unimpl(vcpu, "ignored wrmsr: 0x%x data 0x%llx\n", |
| - msr, data); |
| + kvm_pr_unimpl_wrmsr(vcpu, msr, data); |
| break; |
| case MSR_AMD64_OSVW_ID_LENGTH: |
| if (!guest_cpuid_has(vcpu, X86_FEATURE_OSVW)) |
| diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h |
| index 9de72586f406..f3554bf05201 100644 |
| --- a/arch/x86/kvm/x86.h |
| +++ b/arch/x86/kvm/x86.h |
| @@ -331,6 +331,18 @@ extern bool report_ignored_msrs; |
| |
| extern bool eager_page_split; |
| |
| +static inline void kvm_pr_unimpl_wrmsr(struct kvm_vcpu *vcpu, u32 msr, u64 data) |
| +{ |
| + if (report_ignored_msrs) |
| + vcpu_unimpl(vcpu, "Unhandled WRMSR(0x%x) = 0x%llx\n", msr, data); |
| +} |
| + |
| +static inline void kvm_pr_unimpl_rdmsr(struct kvm_vcpu *vcpu, u32 msr) |
| +{ |
| + if (report_ignored_msrs) |
| + vcpu_unimpl(vcpu, "Unhandled RDMSR(0x%x)\n", msr); |
| +} |
| + |
| static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec) |
| { |
| return pvclock_scale_delta(nsec, vcpu->arch.virtual_tsc_mult, |
| -- |
| 2.50.1 |
| |
