Re: [PATCH v2 07/36] x86/entry/64/compat: After SYSENTER, move STI after the NT fixup

[Denys Vlasenko]

On 10/09/2015 09:48 PM, Andy Lutomirski wrote:
> Anyway, it's still a win, but I'll keep playing.  There may be even
> better ways to do this.

Such as this?
Drop OR, check for cleared IF here:

        testl   $X86_EFLAGS_NT, EFLAGS(%rsp)
        jnz     sysenter_fix_flags
        testl   $X86_EFLAGS_IF, EFLAGS(%rsp)
        jz      sysenter_fix_flags
sysenter_flags_fixed:

and make sysenter_fix_flags code set IF in addition to TF clearing.
This way, we don't even have an unconditional RMW op.

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