Re: [PATCH] x86/asm: Add support for MOVDIR64B instruction

Luck, Tony
2019-08-01T19:49:50Z

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?

-Tony