linux-kernel - Re: [PATCH v11 04/12] x86/mm: get INVLPGB count max from CPUID

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Message-ID: <33e34670-3c24-46d4-9c26-c05a03a8a1b0@intel.com>
Date: Fri, 14 Feb 2025 10:16:55 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Rik van Riel <riel@...riel.com>, x86@...nel.org
Cc: linux-kernel@...r.kernel.org, bp@...en8.de, peterz@...radead.org,
 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, jackmanb@...gle.com,
 jannh@...gle.com, mhklinux@...look.com, andrew.cooper3@...rix.com,
 Manali Shukla <Manali.Shukla@....com>
Subject: Re: [PATCH v11 04/12] x86/mm: get INVLPGB count max from CPUID

On 2/13/25 08:13, Rik van Riel wrote:
> +	/* Max number of pages INVLPGB can invalidate in one shot */
> +	if (boot_cpu_has(X86_FEATURE_INVLPGB)) {
> +		cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
> +		invlpgb_count_max = (edx & 0xffff) + 1;
> +	}
>  }

My only nit with this is that this adds a seventh place that the kernel
reads leaf 0x80000008. The users seem really random, though. Some
cross-vendor stuff, some very AMD-specific stuff.

So, I'll leave that at a nit since I don't have a good suggestion for
solving it:

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>