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| author | Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp> | 2010-02-05 17:52:46 +0900 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2010-03-01 12:36:09 -0300 |
| commit | 1976d2d2c91246a37fcb8246b811de735aa6e9a4 (patch) | |
| tree | b4e12a5300fee56dafb59ad3b3d410d92a3b5f63 /arch | |
| parent | 6316e1c8c6af6ccb55ff8564231710660608f46c (diff) | |
| download | op-kernel-dev-1976d2d2c91246a37fcb8246b811de735aa6e9a4.zip op-kernel-dev-1976d2d2c91246a37fcb8246b811de735aa6e9a4.tar.gz | |
KVM: Remove redundant reading of rax on OUT instructions
kvm_emulate_pio() and complete_pio() both read out the
RAX register value and copy it to a place into which
the value read out from the port will be copied later.
This patch removes this redundancy.
/*** snippet from arch/x86/kvm/x86.c ***/
int complete_pio(struct kvm_vcpu *vcpu)
{
...
if (!io->string) {
if (io->in) {
val = kvm_register_read(vcpu, VCPU_REGS_RAX);
memcpy(&val, vcpu->arch.pio_data, io->size);
kvm_register_write(vcpu, VCPU_REGS_RAX, val);
}
...
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/x86.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c91007f..bd3161c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3551,8 +3551,10 @@ int kvm_emulate_pio(struct kvm_vcpu *vcpu, int in, int size, unsigned port) trace_kvm_pio(vcpu->run->io.direction == KVM_EXIT_IO_OUT, port, size, 1); - val = kvm_register_read(vcpu, VCPU_REGS_RAX); - memcpy(vcpu->arch.pio_data, &val, 4); + if (!vcpu->arch.pio.in) { + val = kvm_register_read(vcpu, VCPU_REGS_RAX); + memcpy(vcpu->arch.pio_data, &val, 4); + } if (!kernel_pio(vcpu, vcpu->arch.pio_data)) { complete_pio(vcpu); |
