----- kernellwp@xxxxxxxxx wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> Linux (among the others) has checks to make sure that certain features
>
> aren't enabled on a certain family/model/stepping if the microcode
> version
> isn't greater than or equal to a known good version.
>
> By exposing the real microcode version, we're preventing buggy guests
> that
> don't check that they are running virtualized (i.e., they should trust
> the
> hypervisor) from disabling features that are effectively not buggy.
>
> Suggested-by: Filippo Sironi <sironi@xxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Liran Alon <liran.alon@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> v1 -> v2:
> * add MSR_IA32_UCODE_REV to emulated_msrs
>
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/x86.c | 9 +++++++--
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> index 938d453..6e13f2f 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -507,6 +507,7 @@ struct kvm_vcpu_arch {
> u64 smi_count;
> bool tpr_access_reporting;
> u64 ia32_xss;
> + u32 microcode_version;
>
> /*
> * Paging state of the vcpu
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 1a3ed81..4ae9517 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1047,6 +1047,7 @@ static u32 emulated_msrs[] = {
> MSR_SMI_COUNT,
> MSR_PLATFORM_INFO,
> MSR_MISC_FEATURES_ENABLES,
> + MSR_IA32_UCODE_REV,
> };
>
> static unsigned num_emulated_msrs;
> @@ -2247,7 +2248,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
>
> switch (msr) {
> case MSR_AMD64_NB_CFG:
> - case MSR_IA32_UCODE_REV:
> case MSR_IA32_UCODE_WRITE:
> case MSR_VM_HSAVE_PA:
> case MSR_AMD64_PATCH_LOADER:
> @@ -2255,6 +2255,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
> case MSR_AMD64_DC_CFG:
> break;
>
> + case MSR_IA32_UCODE_REV:
> + if (msr_info->host_initiated)
> + vcpu->arch.microcode_version = data >> 32;
> + break;
> case MSR_EFER:
> return set_efer(vcpu, data);
> case MSR_K7_HWCR:
> @@ -2550,7 +2554,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu,
> struct msr_data *msr_info)
> msr_info->data = 0;
> break;
> case MSR_IA32_UCODE_REV:
> - msr_info->data = 0x100000000ULL;
> + msr_info->data = (u64)vcpu->arch.microcode_version << 32;
> break;
> case MSR_MTRRcap:
> case 0x200 ... 0x2ff:
> @@ -8232,6 +8236,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool
> init_event)
> vcpu->arch.regs_dirty = ~0;
>
> vcpu->arch.ia32_xss = 0;
> + vcpu->arch.microcode_version = 0x1;
>
> kvm_x86_ops->vcpu_reset(vcpu, init_event);
> }
> --
> 2.7.4
Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx>
