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KVM: VMX: Skip Posted Interrupt updates if APICv is hard disabled

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Explicitly skip posted interrupt updates if APICv is disabled in all of
KVM, or if the guest doesn't have an in-kernel APIC.  The PI descriptor
is kept up-to-date if APICv is inhibited, e.g. so that re-enabling APICv
doesn't require a bunch of updates, but neither the module param nor the
APIC type can be changed on-the-fly.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-21-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-10-08 19:12:13 -07:00 committed by Paolo Bonzini
parent d92a5d1c6c
commit 057aa61bc9
1 changed files with 7 additions and 4 deletions
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11
arch/x86/kvm/vmx/posted_intr.c
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@ -29,11 +29,14 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
unsigned int dest;
/*
* In case of hot-plug or hot-unplug, we may have to undo
* vmx_vcpu_pi_put even if there is no assigned device. And we
* always keep PI.NDST up to date for simplicity: it makes the
* code easier, and CPU migration is not a fast path.
* To simplify hot-plug and dynamic toggling of APICv, keep PI.NDST and
* PI.SN up-to-date even if there is no assigned device or if APICv is
* deactivated due to a dynamic inhibit bit, e.g. for Hyper-V's SyncIC.
*/
if (!enable_apicv || !lapic_in_kernel(vcpu))
return;
/* Nothing to do if PI.SN and PI.NDST both have the desired value. */
if (!pi_test_sn(pi_desc) && vcpu->cpu == cpu)
return;