On Tue, 2021-05-04 at 10:17 -0700, Sean Christopherson wrote:
> Allow userspace to enable RDPID for a guest without also enabling RDTSCP.
> Aside from checking for RDPID support in the obvious flows, VMX also needs
> to set ENABLE_RDTSCP=1 when RDPID is exposed.
>
> For the record, there is no known scenario where enabling RDPID without
> RDTSCP is desirable. But, both AMD and Intel architectures allow for the
> condition, i.e. this is purely to make KVM more architecturally accurate.
>
> Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> arch/x86/kvm/svm/svm.c | 6 ++++--
> arch/x86/kvm/vmx/vmx.c | 27 +++++++++++++++++++++++----
> arch/x86/kvm/x86.c | 3 ++-
> 3 files changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index b3153d40cc4d..231b9650d864 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2669,7 +2669,8 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> if (tsc_aux_uret_slot < 0)
> return 1;
> if (!msr_info->host_initiated &&
> - !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
> return 1;
> msr_info->data = svm->tsc_aux;
> break;
> @@ -2891,7 +2892,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
> return 1;
>
> if (!msr->host_initiated &&
> - !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
> return 1;
>
> /*
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 990ee339a05f..42e4bbaa299a 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1788,7 +1788,8 @@ static void setup_msrs(struct vcpu_vmx *vmx)
> if (update_transition_efer(vmx))
> vmx_setup_uret_msr(vmx, MSR_EFER);
>
> - if (guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDTSCP))
> + if (guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDTSCP) ||
> + guest_cpuid_has(&vmx->vcpu, X86_FEATURE_RDPID))
> vmx_setup_uret_msr(vmx, MSR_TSC_AUX);
>
> vmx_setup_uret_msr(vmx, MSR_IA32_TSX_CTRL);
> @@ -1994,7 +1995,8 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> break;
> case MSR_TSC_AUX:
> if (!msr_info->host_initiated &&
> - !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
> return 1;
> goto find_uret_msr;
> case MSR_IA32_DEBUGCTLMSR:
> @@ -2314,7 +2316,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> break;
> case MSR_TSC_AUX:
> if (!msr_info->host_initiated &&
> - !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
> return 1;
> /* Check reserved bit, higher 32 bits should be zero */
> if ((data >> 32) != 0)
> @@ -4368,7 +4371,23 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
> xsaves_enabled, false);
> }
>
> - vmx_adjust_sec_exec_feature(vmx, &exec_control, rdtscp, RDTSCP);
> + /*
> + * RDPID is also gated by ENABLE_RDTSCP, turn on the control if either
> + * feature is exposed to the guest. This creates a virtualization hole
> + * if both are supported in hardware but only one is exposed to the
> + * guest, but letting the guest execute RDTSCP or RDPID when either one
> + * is advertised is preferable to emulating the advertised instruction
> + * in KVM on #UD, and obviously better than incorrectly injecting #UD.
> + */
> + if (cpu_has_vmx_rdtscp()) {
> + bool rdpid_or_rdtscp_enabled =
> + guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) ||
> + guest_cpuid_has(vcpu, X86_FEATURE_RDPID);
> +
> + vmx_adjust_secondary_exec_control(vmx, &exec_control,
> + SECONDARY_EXEC_ENABLE_RDTSCP,
> + rdpid_or_rdtscp_enabled, false);
> + }
> vmx_adjust_sec_exec_feature(vmx, &exec_control, invpcid, INVPCID);
>
> vmx_adjust_sec_exec_exiting(vmx, &exec_control, rdrand, RDRAND);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e304447be42d..b4516d303413 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5978,7 +5978,8 @@ static void kvm_init_msr_list(void)
> continue;
> break;
> case MSR_TSC_AUX:
> - if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
> + if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP) &&
> + !kvm_cpu_cap_has(X86_FEATURE_RDPID))
> continue;
> break;
> case MSR_IA32_UMWAIT_CONTROL:
Reviewed-by : Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
