Re: [PATCH 15/16] x86: entry.S: simplify optimistic SYSRET

[Ingo Molnar]

* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> From: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
> 
> Avoid redundant load of %r11 (it is already loaded a few instructions before).

Note, this comment is incorrect:

> Do not needlessly increment %rsp - we are going to return to 
> userspace via SYSRET, this insn doesn't use stack for return.

The reason we don't need to increment %rsp because in the very next 
instruction we are restoring it, and then do we execute a SYSRET:

So instead of:

	add $0x80, %rsp
	mov 0x18(%rsp), %rsp

we can do a simplified:

	mov 0x98(%rsp), %rsp

to get the same result.

(I've clarified the changelog with this when applying the patch.)

Thanks,

	Ingo
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