On Tue, Apr 12, 2011 at 03:27:40PM +0300, Avi Kivity wrote:
> On 04/12/2011 03:22 PM, Gleb Natapov wrote:
> >On Tue, Apr 12, 2011 at 03:19:00PM +0300, Avi Kivity wrote:
> >> On 04/12/2011 12:36 PM, Gleb Natapov wrote:
> >> >mmio_index should be taken into account when copying data from
> >> >userspace.
> >> >
> >> >Signed-off-by: Gleb Natapov<gleb@xxxxxxxxxx>
> >> >---
> >> > arch/x86/kvm/x86.c | 3 ++-
> >> > 1 files changed, 2 insertions(+), 1 deletions(-)
> >> >
> >> >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >> >index b568779..609c7ab 100644
> >> >--- a/arch/x86/kvm/x86.c
> >> >+++ b/arch/x86/kvm/x86.c
> >> >@@ -5518,7 +5518,8 @@ static int complete_mmio(struct kvm_vcpu *vcpu)
> >> > if (vcpu->mmio_needed) {
> >> > vcpu->mmio_needed = 0;
> >> > if (!vcpu->mmio_is_write)
> >> >- memcpy(vcpu->mmio_data, run->mmio.data, 8);
> >> >+ memcpy(vcpu->mmio_data + vcpu->mmio_index,
> >> >+ run->mmio.data, 8);
> >> > vcpu->mmio_index += 8;
> >> > if (vcpu->mmio_index< vcpu->mmio_size) {
> >> > run->exit_reason = KVM_EXIT_MMIO;
> >>
> >> Interesting, the code passed the emulator.flat sse test. Does it now?
> >>
> >It pass now and before. Probably by chance.
>
> I don't understand how. I explicitly set the values so that it
> would fail in that case.
>
> Can you patch the test to fail with the current code?
>
If I understand correctly you've already found the explanation why
test case worked?
> >But if I change read_emulated() to do
> >
> > int n = min(size, (unsigned)KVM_MMIO_SIZE);
> >
> >instead of
> >
> > int n = min(size, 8u);
> >
> >emulator.flat fails to emulate far jump instruction.
>
> Ouch, looks like we have the multi-transaction support in two
> places. I guess this is what made sse mmio work.
>
> Not sure what we should do (patch is fine, question is how to
> resolve the duplication).
>
Multi-transaction works faster in complete_mmio, so read_emulated()
should use it by doing int n = min(size, (unsigned)KVM_MMIO_SIZE).
Other code in read_emulated() is still needed since it provides read
re-play for multiple mmio reads during instruction emulation.
--
Gleb.
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