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SubjectRe: [PATCH 2/2] deal with interrupt shadow state for emulated instruction
Glauber Costa wrote:
> we currently unblock shadow interrupt state when we skip an instruction,
> but failing to do so when we actually emulate one. This blocks interrupts
> in key instruction blocks, in particular sti; hlt; sequences
>
> If the instruction emulated is an sti, we have to block shadow interrupts.
> The same goes for mov ss. pop ss also needs it, but we don't currently
> emulate it.
>
> Without this patch, I cannot boot gpxe option roms at vmx machines.
> This is described at https://bugzilla.redhat.com/show_bug.cgi?id=494469
>
> @@ -1618,6 +1620,15 @@ special_insn:
> int err;
>
> sel = c->src.val;
> + if (c->modrm_reg == VCPU_SREG_SS) {
> + u32 int_shadow =
> + kvm_x86_ops->get_interrupt_shadow(ctxt->vcpu,
> + X86_SHADOW_INT_MOV_SS);
> + /* See sti emulation for an explanation of this */
> + if (!(int_shadow & X86_SHADOW_INT_MOV_SS))
> + ctxt->interruptibility = X86_SHADOW_INT_MOV_SS;
> + }
>

The indentation of the first statement here is annoying. Suggest a
function toggle_interruptibility(ctxt, mask). Would eliminate the need
for the comment forward reference as well.


--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.



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