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SubjectRe: [PATCH 2/4] kvm: vmx: Raise #UD on unsupported RDRAND
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On 24.08.2017 15:37, Paolo Bonzini wrote:
> From: Jim Mattson <jmattson@google.com>
>
> A guest may not be configured to support RDRAND, even when the host
> does. If the guest does not support RDRAND, intercept the instruction
> and synthesize #UD. Also clear the "allowed-1" bit for RDRAND exiting
> in the IA32_VMX_PROCBASED_CTLS2 MSR.
>
> Signed-off-by: Jim Mattson <jmattson@google.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/vmx.c | 31 ++++++++++++++++++++++++++++++-
> 1 file changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 08381a5d8879..1f2c69de7872 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2818,7 +2818,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
> vmx->nested.nested_vmx_secondary_ctls_high);
> vmx->nested.nested_vmx_secondary_ctls_low = 0;
> vmx->nested.nested_vmx_secondary_ctls_high &=
> - SECONDARY_EXEC_RDRAND | SECONDARY_EXEC_RDSEED |
> + SECONDARY_EXEC_RDSEED |
> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
> SECONDARY_EXEC_DESC |
> SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
> @@ -3671,6 +3671,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
> SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
> SECONDARY_EXEC_SHADOW_VMCS |
> SECONDARY_EXEC_XSAVES |
> + SECONDARY_EXEC_RDRAND |
> SECONDARY_EXEC_ENABLE_PML |
> SECONDARY_EXEC_TSC_SCALING |
> SECONDARY_EXEC_ENABLE_VMFUNC;
> @@ -5273,6 +5274,12 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx)
> return exec_control;
> }
>
> +static bool vmx_rdrand_supported(void)
> +{
> + return vmcs_config.cpu_based_2nd_exec_ctrl &
> + SECONDARY_EXEC_RDRAND;
> +}
> +
> static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
> {
> struct kvm_vcpu *vcpu = &vmx->vcpu;
> @@ -5342,6 +5349,21 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
> }
> }
>
> + if (vmx_rdrand_supported()) {
> + bool rdrand_enabled = guest_cpuid_has(vcpu, X86_FEATURE_RDRAND);
> + if (rdrand_enabled)
> + exec_control &= ~SECONDARY_EXEC_RDRAND;
> +
> + if (nested) {
> + if (rdrand_enabled)
> + vmx->nested.nested_vmx_secondary_ctls_high |=
> + SECONDARY_EXEC_RDRAND;
> + else
> + vmx->nested.nested_vmx_secondary_ctls_high &=
> + ~SECONDARY_EXEC_RDRAND;
> + }
> + }
> +
> vmx->secondary_exec_control = exec_control;
> }
>
> @@ -6847,6 +6869,12 @@ static int handle_mwait(struct kvm_vcpu *vcpu)
> return handle_nop(vcpu);
> }
>
> +static int handle_invalid_op(struct kvm_vcpu *vcpu)
> +{
> + kvm_queue_exception(vcpu, UD_VECTOR);
> + return 1;
> +}
> +
> static int handle_monitor_trap(struct kvm_vcpu *vcpu)
> {
> return 1;
> @@ -8090,6 +8118,7 @@ static int (*const kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
> [EXIT_REASON_MONITOR_INSTRUCTION] = handle_monitor,
> [EXIT_REASON_INVEPT] = handle_invept,
> [EXIT_REASON_INVVPID] = handle_invvpid,
> + [EXIT_REASON_RDRAND] = handle_invalid_op,
> [EXIT_REASON_XSAVES] = handle_xsaves,
> [EXIT_REASON_XRSTORS] = handle_xrstors,
> [EXIT_REASON_PML_FULL] = handle_pml_full,
>

Reviewed-by: David Hildenbrand <david@redhat.com>

--

Thanks,

David

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