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author | Sean Christopherson <seanjc@google.com> | 2021-12-08 04:52:14 +0300 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-01-19 20:14:37 +0300 |
commit | d76fb40637fc0e84b27bf431cd72cf8fe3f813ef (patch) | |
tree | 28d138efd4da8a43124e363f5302eb7903d25fcc /virt/kvm | |
parent | 4f5a884fc212d99654e4fb36ba98d5354f0dd18e (diff) | |
download | linux-d76fb40637fc0e84b27bf431cd72cf8fe3f813ef.tar.xz |
KVM: VMX: Handle PI descriptor updates during vcpu_put/load
Move the posted interrupt pre/post_block logic into vcpu_put/load
respectively, using the kvm_vcpu_is_blocking() to determining whether or
not the wakeup handler needs to be set (and unset). This avoids updating
the PI descriptor if halt-polling is successful, reduces the number of
touchpoints for updating the descriptor, and eliminates the confusing
behavior of intentionally leaving a "stale" PI.NDST when a blocking vCPU
is scheduled back in after preemption.
The downside is that KVM will do the PID update twice if the vCPU is
preempted after prepare_to_rcuwait() but before schedule(), but that's a
rare case (and non-existent on !PREEMPT kernels).
The notable wart is the need to send a self-IPI on the wakeup vector if
an outstanding notification is pending after configuring the wakeup
vector. Ideally, KVM would just do a kvm_vcpu_wake_up() in this case,
but the scheduler doesn't support waking a task from its preemption
notifier callback, i.e. while the task is right in the middle of
being scheduled out.
Note, setting the wakeup vector before halt-polling is not necessary:
once the pending IRQ will be recorded in the PIR, kvm_vcpu_has_events()
will detect this (via kvm_cpu_get_interrupt(), kvm_apic_get_interrupt(),
apic_has_interrupt_for_ppr() and finally vmx_sync_pir_to_irr()) and
terminate the polling.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20211208015236.1616697-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt/kvm')
0 files changed, 0 insertions, 0 deletions