Re: [PATCH v4 1/5] x86/asm: move the raw asm in iosubmit_cmds512() to special_insns.h

[Dave Jiang]

On 9/23/2020 3:41 AM, Borislav Petkov wrote:
> > Subject: Re: [PATCH v4 1/5] x86/asm: move the raw asm in iosubmit_cmds512() to special_insns.h
>
> Start patch name with a capital letter: "Move the asm definition.."
>
> Also, calling stuff "raw" and "core" is misleading in the kernel context
> - you wanna say simply: "Carve out a generic movdir64b() helper... "

Ok I will update

> On Thu, Sep 17, 2020 at 02:15:16PM -0700, Dave Jiang wrote:
> > diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
> > index 59a3e13204c3..7bc8e714f37e 100644
> > --- a/arch/x86/include/asm/special_insns.h
> > +++ b/arch/x86/include/asm/special_insns.h
> > @@ -234,6 +234,23 @@ static inline void clwb(volatile void *__p)
> >   
> >   #define nop() asm volatile ("nop")
> >   
> > +static inline void movdir64b(void *__dst, const void *src)
>
> Make __dst be the function local variable name and keep "dst", i.e.,
> without the underscores, the function parameter name.

Ok will fix

> > +	/*
> > +	 * Note that this isn't an "on-stack copy", just definition of "dst"
> > +	 * as a pointer to 64-bytes of stuff that is going to be overwritten.
> > +	 * In the MOVDIR64B case that may be needed as you can use the
> > +	 * MOVDIR64B instruction to copy arbitrary memory around. This trick
> > +	 * lets the compiler know how much gets clobbered.
> > +	 */
> > +	volatile struct { char _[64]; } *dst = __dst;
> > +
> > +	/* MOVDIR64B [rdx], rax */
> > +	asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
> > +		     : "=m" (dst)
> > +		     : "d" (src), "a" (dst));
> > +}
> > +
> >   #endif /* __KERNEL__ */
> >   
> >   #endif /* _ASM_X86_SPECIAL_INSNS_H */