On Tue, 2022-03-08 at 10:39 -0600, Suravee Suthikulpanit wrote:
> In X2APIC mode the Logical Destination Register is read-only,
> which provides a fixed mapping between the logical and physical
> APIC IDs. Therefore, there is no Logical APIC ID table in X2AVIC
> and the processor uses the X2APIC ID in the backing page to create
> a vCPU’s logical ID. Also, when x2AVIC is activated, a guest write
> to the x2APIC LDR register would result in #GP injection into
> the guest by the hardware.
>
> Therefore, add logic to check x2APIC mode before updating logical
> APIC ID table.
>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> ---
> arch/x86/kvm/svm/avic.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 5329b93dc4cd..4d7a8743196e 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -406,6 +406,10 @@ static int avic_ldr_write(struct kvm_vcpu *vcpu, u8 g_physical_id, u32 ldr)
> bool flat;
> u32 *entry, new_entry;
>
> + /* Note: x2AVIC does not use logical APIC ID table */
> + if (apic_x2apic_mode(vcpu->arch.apic))
> + return 0;
> +
> flat = kvm_lapic_get_reg(vcpu->arch.apic, APIC_DFR) == APIC_DFR_FLAT;
> entry = avic_get_logical_id_entry(vcpu, ldr, flat);
> if (!entry)
> @@ -424,8 +428,13 @@ static void avic_invalidate_logical_id_entry(struct kvm_vcpu *vcpu)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
> bool flat = svm->dfr_reg == APIC_DFR_FLAT;
> - u32 *entry = avic_get_logical_id_entry(vcpu, svm->ldr_reg, flat);
> + u32 *entry;
> +
> + /* Note: x2AVIC does not use logical APIC ID table */
> + if (apic_x2apic_mode(vcpu->arch.apic))
> + return;
>
> + entry = avic_get_logical_id_entry(vcpu, svm->ldr_reg, flat);
> if (entry)
> clear_bit(AVIC_LOGICAL_ID_ENTRY_VALID_BIT, (unsigned long *)entry);
> }
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
