On Sun, Dec 8, 2024 at 5:11 PM Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> wrote:
>
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Inhibit APICv for TDX guest in KVM since TDX doesn't support APICv accesses
> from host VMM.
>
> Follow how SEV inhibits APICv. I.e, define a new inhibit reason for TDX, set
> it on TD initialization, and add the flag to kvm_x86_ops.required_apicv_inhibits.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> Signed-off-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
> ---
> TDX interrupts breakout:
> - Removed WARN_ON_ONCE(kvm_apicv_activated(vcpu->kvm)) in
> tdx_td_vcpu_init(). (Rick)
> - Change APICV -> APICv in changelog for consistency.
> - Split the changelog to 2 paragraphs.
> ---
> arch/x86/include/asm/kvm_host.h | 12 +++++++++++-
> arch/x86/kvm/vmx/main.c | 3 ++-
> arch/x86/kvm/vmx/tdx.c | 3 +++
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 32c7d58a5d68..df535f08e004 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1281,6 +1281,15 @@ enum kvm_apicv_inhibit {
> */
> APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED,
>
> + /*********************************************************/
> + /* INHIBITs that are relevant only to the Intel's APICv. */
> + /*********************************************************/
> +
> + /*
> + * APICv is disabled because TDX doesn't support it.
> + */
> + APICV_INHIBIT_REASON_TDX,
> +
> NR_APICV_INHIBIT_REASONS,
> };
>
> @@ -1299,7 +1308,8 @@ enum kvm_apicv_inhibit {
> __APICV_INHIBIT_REASON(IRQWIN), \
> __APICV_INHIBIT_REASON(PIT_REINJ), \
> __APICV_INHIBIT_REASON(SEV), \
> - __APICV_INHIBIT_REASON(LOGICAL_ID_ALIASED)
> + __APICV_INHIBIT_REASON(LOGICAL_ID_ALIASED), \
> + __APICV_INHIBIT_REASON(TDX)
>
> struct kvm_arch {
> unsigned long n_used_mmu_pages;
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 7f933f821188..13a0ab0a520c 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -445,7 +445,8 @@ static int vt_gmem_private_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn)
> BIT(APICV_INHIBIT_REASON_BLOCKIRQ) | \
> BIT(APICV_INHIBIT_REASON_PHYSICAL_ID_ALIASED) | \
> BIT(APICV_INHIBIT_REASON_APIC_ID_MODIFIED) | \
> - BIT(APICV_INHIBIT_REASON_APIC_BASE_MODIFIED))
> + BIT(APICV_INHIBIT_REASON_APIC_BASE_MODIFIED) | \
> + BIT(APICV_INHIBIT_REASON_TDX))
>
> struct kvm_x86_ops vt_x86_ops __initdata = {
> .name = KBUILD_MODNAME,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index b0f525069ebd..b51d2416acfb 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -2143,6 +2143,8 @@ static int __tdx_td_init(struct kvm *kvm, struct td_params *td_params,
> goto teardown;
> }
>
> + kvm_set_apicv_inhibit(kvm, APICV_INHIBIT_REASON_TDX);
> +
> return 0;
>
> /*
> @@ -2528,6 +2530,7 @@ static int tdx_td_vcpu_init(struct kvm_vcpu *vcpu, u64 vcpu_rcx)
> return -EIO;
> }
>
> + vcpu->arch.apic->apicv_active = false;
With this setting, apic_timer_expired[1] will always cause timer
interrupts to be pending without injecting them right away. Injecting
it after VM exit [2] could cause unbounded delays to timer interrupt
injection.
[1] https://git.kernel.org/pub/scm/virt/kvm/kvm.git/tree/arch/x86/kvm/lapic.c?h=kvm-coco-queue#n1922
[2] https://git.kernel.org/pub/scm/virt/kvm/kvm.git/tree/arch/x86/kvm/x86.c?h=kvm-coco-queue#n11263
> vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
>
> return 0;
> --
> 2.46.0
>
>
