Handle host initiated FRED MSR access requests to allow FRED context to be set/get from user level.
During VM save/restore and live migration, FRED context needs to be saved/restored, which requires FRED MSRs to be accessed from a user level application, e.g., Qemu. Note, handling of MSR_IA32_FRED_SSP0, i.e., MSR_IA32_PL0_SSP, is not added yet, which is done in the KVM CET patch set. Signed-off-by: Xin Li <[email protected]> Tested-by: Shan Kang <[email protected]> --- Changes since v1: * Use kvm_cpu_cap_has() instead of cpu_feature_enabled() (Chao Gao). * Fail host requested FRED MSRs access if KVM cannot virtualize FRED (Chao Gao). * Handle the case FRED MSRs are valid but KVM cannot virtualize FRED (Chao Gao). * Add sanity checks when writing to FRED MSRs. --- arch/x86/kvm/vmx/vmx.c | 72 ++++++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/x86.c | 47 +++++++++++++++++++++++++++ 2 files changed, 119 insertions(+) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 264378c3b784..ee61d2c25cb0 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1420,6 +1420,24 @@ static void vmx_write_guest_kernel_gs_base(struct vcpu_vmx *vmx, u64 data) preempt_enable(); vmx->msr_guest_kernel_gs_base = data; } + +static u64 vmx_read_guest_fred_rsp0(struct vcpu_vmx *vmx) +{ + preempt_disable(); + if (vmx->guest_state_loaded) + vmx->msr_guest_fred_rsp0 = read_msr(MSR_IA32_FRED_RSP0); + preempt_enable(); + return vmx->msr_guest_fred_rsp0; +} + +static void vmx_write_guest_fred_rsp0(struct vcpu_vmx *vmx, u64 data) +{ + preempt_disable(); + if (vmx->guest_state_loaded) + wrmsrl(MSR_IA32_FRED_RSP0, data); + preempt_enable(); + vmx->msr_guest_fred_rsp0 = data; +} #endif void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, @@ -2019,6 +2037,33 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_KERNEL_GS_BASE: msr_info->data = vmx_read_guest_kernel_gs_base(vmx); break; + case MSR_IA32_FRED_RSP0: + msr_info->data = vmx_read_guest_fred_rsp0(vmx); + break; + case MSR_IA32_FRED_RSP1: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_RSP1); + break; + case MSR_IA32_FRED_RSP2: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_RSP2); + break; + case MSR_IA32_FRED_RSP3: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_RSP3); + break; + case MSR_IA32_FRED_STKLVLS: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_STKLVLS); + break; + case MSR_IA32_FRED_SSP1: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_SSP1); + break; + case MSR_IA32_FRED_SSP2: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_SSP2); + break; + case MSR_IA32_FRED_SSP3: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_SSP3); + break; + case MSR_IA32_FRED_CONFIG: + msr_info->data = vmcs_read64(GUEST_IA32_FRED_CONFIG); + break; #endif case MSR_EFER: return kvm_get_msr_common(vcpu, msr_info); @@ -2226,6 +2271,33 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) vmx_update_exception_bitmap(vcpu); } break; + case MSR_IA32_FRED_RSP0: + vmx_write_guest_fred_rsp0(vmx, data); + break; + case MSR_IA32_FRED_RSP1: + vmcs_write64(GUEST_IA32_FRED_RSP1, data); + break; + case MSR_IA32_FRED_RSP2: + vmcs_write64(GUEST_IA32_FRED_RSP2, data); + break; + case MSR_IA32_FRED_RSP3: + vmcs_write64(GUEST_IA32_FRED_RSP3, data); + break; + case MSR_IA32_FRED_STKLVLS: + vmcs_write64(GUEST_IA32_FRED_STKLVLS, data); + break; + case MSR_IA32_FRED_SSP1: + vmcs_write64(GUEST_IA32_FRED_SSP1, data); + break; + case MSR_IA32_FRED_SSP2: + vmcs_write64(GUEST_IA32_FRED_SSP2, data); + break; + case MSR_IA32_FRED_SSP3: + vmcs_write64(GUEST_IA32_FRED_SSP3, data); + break; + case MSR_IA32_FRED_CONFIG: + vmcs_write64(GUEST_IA32_FRED_CONFIG, data); + break; #endif case MSR_IA32_SYSENTER_CS: if (is_guest_mode(vcpu)) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 363b1c080205..4e8d60f248e3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1451,6 +1451,9 @@ static const u32 msrs_to_save_base[] = { MSR_STAR, #ifdef CONFIG_X86_64 MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR, + MSR_IA32_FRED_RSP0, MSR_IA32_FRED_RSP1, MSR_IA32_FRED_RSP2, + MSR_IA32_FRED_RSP3, MSR_IA32_FRED_STKLVLS, MSR_IA32_FRED_SSP1, + MSR_IA32_FRED_SSP2, MSR_IA32_FRED_SSP3, MSR_IA32_FRED_CONFIG, #endif MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA, MSR_IA32_FEAT_CTL, MSR_IA32_BNDCFGS, MSR_TSC_AUX, @@ -1892,6 +1895,30 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data, return 1; data = (u32)data; + break; + case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG: + if (index != MSR_IA32_FRED_STKLVLS && is_noncanonical_address(data, vcpu)) + return 1; + if ((index >= MSR_IA32_FRED_RSP0 && index <= MSR_IA32_FRED_RSP3) && + (data & GENMASK_ULL(5, 0))) + return 1; + if ((index >= MSR_IA32_FRED_SSP1 && index <= MSR_IA32_FRED_SSP3) && + (data & GENMASK_ULL(2, 0))) + return 1; + + if (host_initiated) { + if (!kvm_cpu_cap_has(X86_FEATURE_FRED)) + return 1; + } else { + /* + * Inject #GP upon FRED MSRs accesses from a non-FRED guest, + * which also ensures no malicious guest can write to FRED + * MSRs to corrupt host FRED MSRs. + */ + if (!guest_can_use(vcpu, X86_FEATURE_FRED)) + return 1; + } + break; } @@ -1936,6 +1963,22 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data, !guest_cpuid_has(vcpu, X86_FEATURE_RDPID)) return 1; break; + case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG: + if (host_initiated) { + if (!kvm_cpu_cap_has(X86_FEATURE_FRED)) + return 1; + } else { + /* + * Inject #GP upon FRED MSRs accesses from a non-FRED guest, + * which also ensures no malicious guest can write to FRED + * MSRs to corrupt host FRED MSRs. + */ + if (!guest_can_use(vcpu, X86_FEATURE_FRED)) + return 1; + } + + break; + } msr.index = index; @@ -7364,6 +7407,10 @@ static void kvm_probe_msr_to_save(u32 msr_index) if (!(kvm_get_arch_capabilities() & ARCH_CAP_TSX_CTRL_MSR)) return; break; + case MSR_IA32_FRED_RSP0 ... MSR_IA32_FRED_CONFIG: + if (!kvm_cpu_cap_has(X86_FEATURE_FRED)) + return; + break; default: break; } -- 2.43.0
