linux-kernel - Re: [PATCH v2 03/29] x86/cpu: Remove leaf 0x2 parsing loop and add helpers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z9iVyrlDbFyI9Rqi@gmail.com>
Date: Mon, 17 Mar 2025 22:36:10 +0100
From: Ingo Molnar <mingo@...nel.org>
To: "Ahmed S. Darwish" <darwi@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	John Ogness <john.ogness@...utronix.de>, x86@...nel.org,
	x86-cpuid@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 03/29] x86/cpu: Remove leaf 0x2 parsing loop and add
 helpers


* Ahmed S. Darwish <darwi@...utronix.de> wrote:

> Leaf 0x2 output includes a "query count" byte where it was supposed to
> specify the number of repeated CPUID leaf 0x2 subleaf 0 queries needed
> to extract all of the hardware's cache and TLB descriptors.
> 
> Per current Intel manuals, all CPUs supporting this leaf "will always"
> return an iteration count of 1.
> 
> Remove the leaf 0x2 query count loop and just query the hardware once.
> Parse the output with C99 bitfields instead of ugly bitwise operations.
> 
> Provide leaf 0x2 parsing helpers with all the above.  Use such helpers
> at x86/cpu intel.c.  Further commits will use them for x86/cacheinfo.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Ahmed S. Darwish <darwi@...utronix.de>
> ---
>  arch/x86/include/asm/cpuid.h              |  1 +
>  arch/x86/include/asm/cpuid/leaf_0x2_api.h | 65 +++++++++++++++++++++++
>  arch/x86/include/asm/cpuid/types.h        | 16 ++++++
>  arch/x86/kernel/cpu/intel.c               | 24 +++------
>  4 files changed, 88 insertions(+), 18 deletions(-)
>  create mode 100644 arch/x86/include/asm/cpuid/leaf_0x2_api.h

Could you please turn this into at least two patches:

  - One does the functional change - this patch should be as small as 
    possible. This patch turns a piece of 'Intel documents' property 
    into 'actual code' that differs from the previous code, which may 
    or may not regress in practice.

  - The other does the factoring out and the introduction of 
    <asm/cpuid/leaf_0x2_api.h>.

Thanks,

	Ingo