Re: [PATCH 1/5] KVM: x86: Emulator does not calculate address correctly

[Nadav Amit]

On 5/7/14, 4:57 PM, Paolo Bonzini wrote:
> Il 07/05/2014 14:32, Nadav Amit ha scritto:
> > In long-mode, when the address size is 4 bytes, the linear address is not
> > truncated as the emulator mistakenly does.  Instead, the offset within
> > the
> > segment (the ea field) should be truncated according to the address size.
> >
> > As Intel SDM says: "In 64-bit mode, the effective address components
> > are added
> > and the effective address is truncated ... before adding the full 64-bit
> > segment base."
> >
> > Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
> > ---
> >  arch/x86/kvm/emulate.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> > index e8a5840..743e8e3 100644
> > --- a/arch/x86/kvm/emulate.c
> > +++ b/arch/x86/kvm/emulate.c
> > @@ -631,7 +631,8 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
> >      u16 sel;
> >      unsigned cpl;
> >
> > -    la = seg_base(ctxt, addr.seg) + addr.ea;
> > +    la = seg_base(ctxt, addr.seg) +
> > +        (ctxt->ad_bytes == 8 ? addr.ea : (u32)addr.ea);
>
> I think you need "fetch || ctxt->ad_bytes == 8" here.
>
> Paolo
Yes. I did not test the fetch scenario.
I intend to do so soon to avoid such mistakes.

Nadav
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