Re: [Xen-devel] [PATCH] x86/emul: Assert the STI shadow when POPF sets the interrupt flag

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.11.18 at 15:09, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -4061,6 +4061,12 @@ x86_emulate(
>              }
>          }
>          dst.val &= EFLAGS_MODIFIABLE;
> +
> +        /* When IF transitions from 0 to 1, assert the STI shadow. */
> +        if ( !(_regs.eflags & X86_EFLAGS_IF) &&
> +             ((dst.val & ~mask) & X86_EFLAGS_IF) )
> +            ctxt->retire.sti = true;

I'm entirely unaware that POPF behaves the same way as STI in this
regard. Therefore: Are you sure? Can you point me to where this is
spelled out?

Jan



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