KVM: host side for eoi optimization

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Implementation of PV EOI using shared memory.
This reduces the number of exits an interrupt
causes as much as by half.

The idea is simple: there's a bit, per APIC, in guest memory,
that tells the guest that it does not need EOI.
We set it before injecting an interrupt and clear
before injecting a nested one. Guest tests it using
a test and clear operation - this is necessary
so that host can detect interrupt nesting -
and if set, it can skip the EOI MSR.

There's a new MSR to set the address of said register
in guest memory. Otherwise not much changed:
- Guest EOI is not required
- Register is tested & ISR is automatically cleared on exit

For testing results see description of previous patch
'kvm_para: guest side for eoi avoidance'.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

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This commit is contained in:

Michael S. Tsirkin 2012-06-24 19:25:07 +03:00 • committed by Avi Kivity

parent d905c06935

commit ae7a2a3fb6

6 changed files with 193 additions and 4 deletions

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12

arch/x86/include/asm/kvm_host.h

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1

arch/x86/kvm/cpuid.c

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141

arch/x86/kvm/lapic.c

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2

arch/x86/kvm/lapic.h

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34

arch/x86/kvm/trace.h

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7

arch/x86/kvm/x86.c

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