Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [patch 12/17] Consistently wrap paravirt ops callsites to make them patchable | Date | Mon, 2 Apr 2007 09:11:50 +0200 |
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On Monday 02 April 2007 07:57, Jeremy Fitzhardinge wrote: > Wrap a set of interesting paravirt_ops calls in a wrapper which makes > the callsites available for patching. Unfortunately this is pretty > ugly because there's no way to get gcc to generate a function call, > but also wrap just the callsite itself with the necessary labels. > > This patch supports functions with 0-4 arguments, and either void or > returning a value. 64-bit arguments must be split into a pair of > 32-bit arguments (lower word first). Small structures are returned in > registers.
Can you please add some comments to the code explaining this a little? Best would be perhaps a overview document in Documentation too.
> +#define PVOP_CALL0(__rettype, __op) \
The __s shouldn't be needed for the macro arguments because there is no shared name space with the caller.
> + ({ \ > + __rettype __ret; \ > + if (sizeof(__rettype) > sizeof(unsigned long)) { \ > + unsigned long long __tmp; \ > + unsigned long __ecx; \ > + asm volatile(paravirt_alt(PARAVIRT_CALL) \
Not having the volatile would probably generate better code, but it seems much safer for now.
> + : "=A" (__tmp), "=c" (__ecx) \ > + : paravirt_type(__op), \ > + paravirt_clobber(CLBR_ANY) \ > + : "memory", "cc"); \
And the cc clobber is also not needed
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