Re: ia32_sysenter_target does not preserve EFLAGS

[Linus Torvalds]

On Fri, Mar 27, 2015 at 1:53 PM, Brian Gerst <brgerst@xxxxxxxxx> wrote:
>> <-- IRQ.  Boom
>
> The sti will delay interrupts for one instruction, and that should include NMIs.

Nope. Intel explicitly documents the NMI case only for mov->ss and popss.

> The Intel SDM states for STI:
> "The IF flag and the STI and CLI instructions do not prohibit the
> generation of exceptions and NMI interrupts. NMI
> interrupts (and SMIs) may be blocked for one macroinstruction following an STI."

Note the *may*. For movss and popss the software developer guide
explicitly says that NMI's are also blocked.

For plain sti, it seems to be dependent on microarchitecture.

                     Linus
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