linux-kernel - Re: [PATCH v6 05/12] x86/mm: add INVLPGB support code

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Message-ID: <cc6101619afe5f148b1575fb42807cb1b4766b6e.camel@surriel.com>
Date: Wed, 22 Jan 2025 11:58:26 -0500
From: Rik van Riel <riel@...riel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, bp@...en8.de, 
	dave.hansen@...ux.intel.com, zhengqi.arch@...edance.com,
 nadav.amit@...il.com, 	thomas.lendacky@....com, kernel-team@...a.com,
 linux-mm@...ck.org, 	akpm@...ux-foundation.org, jannh@...gle.com,
 mhklinux@...look.com, 	andrew.cooper3@...rix.com
Subject: Re: [PATCH v6 05/12] x86/mm: add INVLPGB support code

On Tue, 2025-01-21 at 10:45 +0100, Peter Zijlstra wrote:
> On Sun, Jan 19, 2025 at 09:40:13PM -0500, Rik van Riel wrote:
> 
> > 
> > +static inline void __invlpgb(unsigned long asid, unsigned long
> > pcid,
> > +			     unsigned long addr, u16 extra_count,
> > +			     bool pmd_stride, unsigned long flags)
> > +{
> > +	u32 edx = (pcid << 16) | asid;
> > +	u32 ecx = (pmd_stride << 31) | extra_count;
> > +	u64 rax = addr | flags;
> > +
> > +	/* INVLPGB; supported in binutils >= 2.36. */
> > +	asm volatile(".byte 0x0f, 0x01, 0xfe" : : "a" (rax), "c"
> > (ecx), "d" (edx));
> > +}
> 
> So asid is always 0 (for now), but I'd feel better if that was a u16
> argument, less chance funnies when someone starts using it.
> 
> We should probably mask or WARN on addr having low bits set, and
> flags
> should then be a u8 or something.

Done and done. Thank you for the suggestions.

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