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KVM: Do not communicate to userspace through cpu registers during PIO

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Currently when passing the a PIO emulation request to userspace, we
rely on userspace updating %rax (on 'in' instructions) and %rsi/%rdi/%rcx
(on string instructions).  This (a) requires two extra ioctls for getting
and setting the registers and (b) is unfriendly to non-x86 archs, when
they get kvm ports.

So fix by doing the register fixups in the kernel and passing to userspace
only an abstract description of the PIO to be done.

Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Avi Kivity
2007-02-22 19:39:30 +02:00
parent 9a2bb7f486
commit 46fc147788
5 changed files with 53 additions and 6 deletions
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2
drivers/kvm/svm.c
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@@ -1037,6 +1037,7 @@ static int io_interception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
kvm_run->io.size = ((io_info & SVM_IOIO_SIZE_MASK) >> SVM_IOIO_SIZE_SHIFT);
kvm_run->io.string = (io_info & SVM_IOIO_STR_MASK) != 0;
kvm_run->io.rep = (io_info & SVM_IOIO_REP_MASK) != 0;
kvm_run->io.count = 1;
if (kvm_run->io.string) {
unsigned addr_mask;
@@ -1056,6 +1057,7 @@ static int io_interception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
}
} else
kvm_run->io.value = vcpu->svm->vmcb->save.rax;
vcpu->pio_pending = 1;
return 0;
}