On 05/04/2014 04:46 PM, Paolo Bonzini wrote:
>
> Your suggested trick of splitting the return paths for IF=0/IF=1 can be
> also done like this:
>
> movq EFLAGS-ARGOFFSET(%rsp), %rdi
> btrq $9, %rdi # Clear IF, save old value in CF
> movq %rdi, (%rsi)
> ...
> popfq
> jnc 1f # If IF was 0, just return
> sti # Using STI gets us an interrupt shadow
> 1f:
> retq
>
That doesn't work, because CF gets restored by the popfq as well.
Unfortunately.
-hpa
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