Messages in this thread | | | Date | Thu, 1 Aug 2019 22:36:14 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/asm: Add support for MOVDIR64B instruction |
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On Thu, Aug 01, 2019 at 11:28:08PM +0300, Kirill A. Shutemov wrote: > On Thu, Aug 01, 2019 at 12:49:48PM -0700, Luck, Tony wrote: > > On Thu, Aug 01, 2019 at 10:43:48PM +0300, Alexey Dobriyan wrote: > > > > +static inline void movdir64b(void *dst, const void *src) > > > > +{ > > > > + /* movdir64b [rdx], rax */ > > > > + asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02" > > > > + : "=m" (*(char *)dst) > > > ^^^^^^^^^^ > > > > > > > + : "d" (src), "a" (dst)); > > > > +} > > > > > > Probably needs fake 64-byte type, so that compiler knows what is dirty. > > > > Would that be something like this? > > > > static inline void movdir64b(void *dst, const void *src) > > { > > struct dstbytes { > > char pad[64]; > > }; > > > > /* movdir64b [rdx], rax */ > > asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02" > > : "=m" (*(struct dstbytes *)dst) > > : "d" (src), "a" (dst)); > > } > > > > Or did you have something else in mind? > > Or should we add "memory" clobber instead, like we do for string > operations?
I think Tony's in the right direction. We already do dst "sizing" like that for the compiler in clwb().
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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