Re: [Qemu-devel] Guest SIGILL when different IO is implemented

[Miltiadis Hatzimihail <hatzimiltos@gmail.com>]

That's great thanks for the clarification.

Is this patch going to make it to the mainline at some point?


Miltiadis Hatzimihail


On Thu, May 11, 2017 at 1:44 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:

>
>
> On 11/05/2017 14:40, Miltiadis Hatzimihail wrote:
> > Thanks Paolo that worked!
> >
> > Btw, this line
> >
> > ​
> > +       GP(SrcMem | DstReg | ModRM | Mov, &pfx_0f_10_0f_11),
> > +       GP(SrcReg | DstMem | ModRM | Mov, &pfx_0f_10_0f_11),
> > -        N, N, N, N, N, N, N, N,
> > +       N, N, N, N, N, N,
> >
> > I think it has 2 extra Ns (not removed from your change?).
>
> Oops, you're right.
>
> > Those instructions were not implemented for a reason or is it simply a
> > chance of never seeing this issue that I saw?
>
> Never seeing this issue.
>
> >>> The interesting thing is that in the ram case the test is passing, but
> in
> >>> the io is failing. Also, if I try this without KVM, it passes in both
> cases.
> >>
> >>Yes, in the RAM case KVM is not invoked at all.
> > So for my benefit, does this mean that any RAM transaction is emulated
> > by QEMU or does it go through KVM to the bare metal? (and hence, KVM is
> > not emulating this?)
>
> The latter.  The don't get any emulation.
>
> Paolo
>
> >
> > ​Milton
> >
> >
> > On Thu, May 11, 2017 at 12:51 PM, Paolo Bonzini <pbonzini@redhat.com
> > <mailto:pbonzini@redhat.com>> wrote:
> >
> >
> >
> >     On 11/05/2017 09:00, Miltiadis Hatzimihail wrote:
> >     >
> >     > The interesting thing is that in the ram case the test is passing,
> but in
> >     > the io is failing. Also, if I try this without KVM, it passes in
> both cases.
> >
> >     Yes, in the RAM case KVM is not invoked at all.
> >
> >     > So I ve done some reading and for the 2 cases above I get:
> >     >
> >     > - KVM_EXIT_MMIO on memory_region_init_io  (KVM attempts and fails
> to
> >     > emulate MOVSS),
> >     > - KVM_EXIT_EXCEPTION on memory_region_init_ram(QEMU emulates MOVSS)
> >
> >     No, you don't get any exit for memory_region_init_ram.
> >
> >     > Is that right?
> >     >
> >     > Now the question is, if I want to use the IO instead of a RAM,
> what's the
> >     > best way to solve this?
> >
> >     Please try this KVM patch:
> >
> >     diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> >     index c25cfaf584e7..53fbd1589d2e 100644
> >     --- a/arch/x86/kvm/emulate.c
> >     +++ b/arch/x86/kvm/emulate.c
> >     @@ -3534,6 +3534,22 @@ static int em_rdpmc(struct x86_emulate_ctxt
> >     *ctxt)
> >             return X86EMUL_CONTINUE;
> >      }
> >
> >     +static int em_movss(struct x86_emulate_ctxt *ctxt)
> >     +{
> >     +       memcpy(ctxt->dst.valptr, ctxt->src.valptr, 4);
> >     +       ctxt->op_bytes = 4;
> >     +       ctxt->dst.bytes = 4;
> >     +       return X86EMUL_CONTINUE;
> >     +}
> >     +
> >     +static int em_movsd(struct x86_emulate_ctxt *ctxt)
> >     +{
> >     +       memcpy(ctxt->dst.valptr, ctxt->src.valptr, 8);
> >     +       ctxt->op_bytes = 8;
> >     +       ctxt->dst.bytes = 8;
> >     +       return X86EMUL_CONTINUE;
> >     +}
> >     +
> >      static int em_mov(struct x86_emulate_ctxt *ctxt)
> >      {
> >             memcpy(ctxt->dst.valptr, ctxt->src.valptr,
> >     sizeof(ctxt->src.valptr));
> >     @@ -4407,6 +4423,11 @@ static int check_perm_out(struct
> >     x86_emulate_ctxt *ctxt)
> >             I(Mmx, em_mov), I(Sse | Aligned, em_mov), N, I(Sse |
> >     Unaligned, em_mov),
> >      };
> >
> >     +static const struct gprefix pfx_0f_10_0f_11 = {
> >     +       I(Sse | Unaligned, em_mov), I(Sse | Unaligned, em_mov),
> >     +       I(Sse, em_movsd), I(Sse, em_movss),
> >     +};
> >     +
> >      static const struct instr_dual instr_dual_0f_2b = {
> >             I(0, em_mov), N
> >      };
> >     @@ -4626,6 +4647,8 @@ static int check_perm_out(struct
> >     x86_emulate_ctxt *ctxt)
> >             DI(ImplicitOps | Priv, invd), DI(ImplicitOps | Priv,
> >     wbinvd), N, N,
> >             N, D(ImplicitOps | ModRM | SrcMem | NoAccess), N, N,
> >             /* 0x10 - 0x1F */
> >     ​​
> >     +       GP(SrcMem | DstReg | ModRM | Mov, &pfx_0f_10_0f_11),
> >     +       GP(SrcReg | DstMem | ModRM | Mov, &pfx_0f_10_0f_11),
> >             N, N, N, N, N, N, N, N,
> >             D(ImplicitOps | ModRM | SrcMem | NoAccess),
> >             N, N, N, N, N, N, D(ImplicitOps | ModRM | SrcMem | NoAccess),
> >
> >     Thanks,
> >
> >     Paolo
> >
> >
>