KVM: PIC: enhance IPI avoidance

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The PIC code makes little effort to avoid kvm_vcpu_kick(), resulting in
unnecessary guest exits in some conditions.

For example, if the timer interrupt is routed through the IOAPIC, IRR
for IRQ 0 will get set but not cleared, since the APIC is handling the
acks.

This means that everytime an interrupt < 16 is triggered, the priority
logic will find IRQ0 pending and send an IPI to vcpu0 (in case IRQ0 is
not masked, which is Linux's case).

Introduce a new variable isr_ack to represent the IRQ's for which the
guest has been signalled / cleared the ISR. Use it to avoid more than
one IPI per trigger-ack cycle, in addition to the avoidance when ISR is
set in get_priority().

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

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This commit is contained in:

Marcelo Tosatti 2008-09-24 20:28:34 -03:00 • committed by Avi Kivity

parent 582801a95d

commit e48258009d

3 changed files with 18 additions and 2 deletions

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17

arch/x86/kvm/i8259.c

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2

arch/x86/kvm/irq.h

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1

arch/x86/kvm/x86.c

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