linux-kernel - Re: [PATCH RFC WIP] x86/paravirt: add register-saving thunks to reduce caller register pressure

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Date:	Wed, 28 Jan 2009 15:17:25 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Zachary Amsden <zach@...are.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC WIP] x86/paravirt: add register-saving thunks to	reduce
 caller register pressure

Zachary Amsden wrote:
>> Standard calling convention is:
>>          arguments          return      scratch
>> x86-32   eax edx ecx        eax         ?
>>     
>
> ecx, edx
>   

OK, no scratch beyond the arg regs.

>> XXX Deal with VMI.  What's their calling convention?
>>     
>
> Enable/Disable have no clobbers at all.
> Save clobbers only return value, %eax
> Restore also clobbers nothing.
>   

OK, they can be plugged in directly then.  Use __PV_IS_CALLEE_SAVE(func) 
to wrap it up in the right type.

> The patching code has gotten quite complex with the 32/64 union; let me
> apply it first and see before I comment on the patch.
>   

OK.  I just posted updated versions of this series, so make sure you 
comment on that one.

    J
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