On Wed, 2022-05-18 at 11:26 -0500, Suravee Suthikulpanit wrote:
> From: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
>
> As a preparation for x2avic, this patch ensures that x2apic msrs
> are always intercepted for the nested guest.
>
> Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> ---
> arch/x86/kvm/svm/nested.c | 5 +++++
> arch/x86/kvm/svm/svm.h | 9 +++++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index f209c1ca540c..b61f8939c210 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -230,6 +230,11 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
> break;
>
> p = msrpm_offsets[i];
> +
> + /* x2apic msrs are intercepted always for the nested guest */
> + if (is_x2apic_msrpm_offset(p))
> + continue;
> +
> offset = svm->nested.ctl.msrpm_base_pa + (p * 4);
>
> if (kvm_vcpu_read_guest(&svm->vcpu, offset, &value, 4))
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 818817b11f53..309445619756 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -517,6 +517,15 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm)
> return svm->nested.ctl.nested_ctl & SVM_NESTED_CTL_NP_ENABLE;
> }
>
> +static inline bool is_x2apic_msrpm_offset(u32 offset)
> +{
> + /* 4 msrs per u8, and 4 u8 in u32 */
> + u32 msr = offset * 16;
> +
> + return (msr >= APIC_BASE_MSR) &&
> + (msr < (APIC_BASE_MSR + 0x100));
> +}
> +
> /* svm.c */
> #define MSR_INVALID 0xffffffffU
>
Just one thing, this patch should be earlier in the series (or even first one),
to avoid having a commit window where the problem exists, where malicious
L1 can get access to L0's apic msrs this way.
Best regards,
Maxim Levitsky
