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

[Paolo Bonzini]

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