KVM: nVMX: Explicitly update vPPR on successful nested VM-Enter

Always request pending event evaluation after successful nested VM-Enter
if L1 has a pending IRQ, as KVM will effectively do so anyways when APICv
is enabled, by way of vmx_has_apicv_interrupt().  This will allow dropping
the aforementioned APICv check, and will also allow handling nested Posted
Interrupt processing entirely within vmx_check_nested_events(), which is
necessary to honor priority between concurrent events.

Note, checking for pending IRQs has a subtle side effect, as it results in
a PPR update for L1's vAPIC (PPR virtualization does happen at VM-Enter,
but for nested VM-Enter that affects L2's vAPIC, not L1's vAPIC).  However,
KVM updates PPR _constantly_, even when PPR technically shouldn't be
refreshed, e.g. kvm_vcpu_has_events() re-evaluates PPR if IRQs are
unblocked, by way of the same kvm_apic_has_interrupt() check.  Ditto for
nested VM-Enter itself, when nested posted interrupts are enabled.  Thus,
trying to avoid a PPR update on VM-Enter just to be pedantically accurate
is ridiculous, given the behavior elsewhere in KVM.

Link: https://lore.kernel.org/kvm/20230312180048.1778187-1-jason.cj.chen@intel.com
Closes: https://lore.kernel.org/all/20240920080012.74405-1-mankku@gmail.com
Signed-off-by: Chao Gao <chao.gao@intel.com>
Link: https://lore.kernel.org/r/20241101191447.1807602-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 103baa8e4cf8def01d7f86ba621c69476d4e0bfe..a8f8ac0f26d2db6ed841e7dcd944ca9244f4bcd9 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3618,7 +3618,8 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
         * effectively unblock various events, e.g. INIT/SIPI cause VM-Exit
         * unconditionally.
         */
-       if (unlikely(evaluate_pending_interrupts))
+       if (unlikely(evaluate_pending_interrupts) ||
+           kvm_apic_has_interrupt(vcpu))
                kvm_make_request(KVM_REQ_EVENT, vcpu);
 
        /*