Re: [Xen-devel] [PATCH 1/4] VMX: streamline entry.S code

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.08.13 at 13:01, Tim Deegan <tim@xxxxxxx> wrote:
> At 15:01 +0100 on 23 Aug (1377270100), Jan Beulich wrote:
>> +ENTRY(vmx_asm_vmexit_handler)
>>          push %rdi
>>          push %rsi
>>          push %rdx
>>          push %rcx
>>          push %rax
>> +        mov  %cr2,%rax
>>          push %r8
>>          push %r9
>>          push %r10
>>          push %r11
>>          push %rbx
>> +        GET_CURRENT(%rbx)
> 
> I see this avoids a potential stall below, but OTOH it introduces an
> explicit %rsp access into a string of push ops, which is frowned on
> (IIRC there's special fast-forwarding of %rsp in chains of pushes).
> I'd be inclined to leave it alone unless there's a measurable
> improvement, since the code's more readable as-is.

I guess I'll leave it this way, aiming at replacing the pushes by moves
(as we did elsewhere in the 4.3 cycle) at some point.

Jan


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