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SubjectRe: [PATCH v2 2/2] KVM: x86/emulator: Emulate RDPID only if it is enabled in guest
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On 3/7/22 13:26, Hou Wenlong wrote:
> When RDTSCP is supported but RDPID is not supported in host,
> RDPID emulation is available. However, __kvm_get_msr() would
> only fail when RDTSCP/RDPID both are disabled in guest, so
> the emulator wouldn't inject a #UD when RDPID is disabled but
> RDTSCP is enabled in guest.
>
> Fixes: fb6d4d340e05 ("KVM: x86: emulate RDPID")
> Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
> ---
> arch/x86/kvm/emulate.c | 4 +++-
> arch/x86/kvm/kvm_emulate.h | 1 +
> arch/x86/kvm/x86.c | 6 ++++++
> 3 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 3497a35bd085..be83c9c8482d 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -3521,8 +3521,10 @@ static int em_rdpid(struct x86_emulate_ctxt *ctxt)
> {
> u64 tsc_aux = 0;
>
> - if (ctxt->ops->get_msr(ctxt, MSR_TSC_AUX, &tsc_aux))
> + if (!ctxt->ops->guest_has_rdpid(ctxt))
> return emulate_ud(ctxt);
> +
> + ctxt->ops->get_msr(ctxt, MSR_TSC_AUX, &tsc_aux);
> ctxt->dst.val = tsc_aux;
> return X86EMUL_CONTINUE;
> }
> diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
> index 29ac5a9679e5..1cbd46cf71f9 100644
> --- a/arch/x86/kvm/kvm_emulate.h
> +++ b/arch/x86/kvm/kvm_emulate.h
> @@ -228,6 +228,7 @@ struct x86_emulate_ops {
> bool (*guest_has_long_mode)(struct x86_emulate_ctxt *ctxt);
> bool (*guest_has_movbe)(struct x86_emulate_ctxt *ctxt);
> bool (*guest_has_fxsr)(struct x86_emulate_ctxt *ctxt);
> + bool (*guest_has_rdpid)(struct x86_emulate_ctxt *ctxt);
>
> void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 09c5677f4186..44f97038d3e5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7723,6 +7723,11 @@ static bool emulator_guest_has_fxsr(struct x86_emulate_ctxt *ctxt)
> return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_FXSR);
> }
>
> +static bool emulator_guest_has_rdpid(struct x86_emulate_ctxt *ctxt)
> +{
> + return guest_cpuid_has(emul_to_vcpu(ctxt), X86_FEATURE_RDPID);
> +}
> +
> static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)
> {
> return kvm_register_read_raw(emul_to_vcpu(ctxt), reg);
> @@ -7807,6 +7812,7 @@ static const struct x86_emulate_ops emulate_ops = {
> .guest_has_long_mode = emulator_guest_has_long_mode,
> .guest_has_movbe = emulator_guest_has_movbe,
> .guest_has_fxsr = emulator_guest_has_fxsr,
> + .guest_has_rdpid = emulator_guest_has_rdpid,
> .set_nmi_mask = emulator_set_nmi_mask,
> .get_hflags = emulator_get_hflags,
> .exiting_smm = emulator_exiting_smm,

Queued, thanks.

Would you try replacing the ->guest_has_... callbacks with just one that
takes an X86_FEATURE_* constant as a second argument?

Paolo

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