All of lore.kernel.org
 help / color / mirror / Atom feed
From: Mauricio Faria de Oliveira <mfo@igalia.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Juergen Gross <jgross@suse.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Jan Beulich <jbeulich@suse.com>, Brian Gerst <brgerst@gmail.com>,
	kernel-dev@igalia.com, linux-kernel@vger.kernel.org,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v9 4/5] x86/cpuid: fix unbootable VMs by really inlining memcmp() in hypervisor_cpuid_base()
Date: Tue, 15 Sep 2026 20:49:27 -0300	[thread overview]
Message-ID: <9086138f2dcaffe30622438b7e825ae7@igalia.com> (raw)
In-Reply-To: <20260915154853.GAaqlo5YxQ9ALlhjbF@fat_crate.local>

On 2026-09-15 12:48, Borislav Petkov wrote:
> On Mon, Sep 14, 2026 at 10:11:55PM -0700, Borislav Petkov wrote:
>> Hmm, never heard that before but that doesn't mean anything. Probably should
>> mention it in one of the commit messages so that we know for the future...
> 
> My compiler friends are telling me that gcc doesn't do that now but it might
> in the future, perhaps.
> 
> -fno-builtin-memcmp
> 
> will stop any of that behavior so if, perhaps, building the pvh code with it
> looks better as a solution, we probably could use it.

It looks like clang does [1], but according to an LLM that is also
disabled with -fno-builtin-memcmp.

IMO a fix in the source file is clearer, less obfuscated than in a
Makefile (and the source file has to be changed anyway). It also has the
potential advantage that, if the Makefile change slips in a future
change/refactor, the issue shouldn't reappear.

Either way, please let me know and I can certainly change the patch.

Thanks,

[1]
https://github.com/llvm/llvm-project/commit/9473c01e968bc4ecf5ea7c54ef0c84b687d365ea

-- 
Mauricio


  reply	other threads:[~2026-09-15 23:50 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-22 18:33 [PATCH v9 0/5] x86/pvh: fix unbootable VMs again (PVH + KASAN) Mauricio Faria de Oliveira
2026-08-22 18:33 ` [PATCH v9 1/5] x86/boot: Remove "cc" clobber from memcmp() Mauricio Faria de Oliveira
2026-09-01 13:16   ` Jan Beulich
2026-09-02  8:33     ` David Laight
2026-09-02 14:18       ` H. Peter Anvin
2026-09-02  2:31   ` Borislav Petkov
2026-09-02 13:29     ` Michael Matz
2026-09-02 13:48       ` Mauricio Faria de Oliveira
2026-09-03  0:01         ` Borislav Petkov
2026-09-03  0:07           ` Mauricio Faria de Oliveira
2026-09-03  0:39             ` Borislav Petkov
2026-09-03  8:40           ` David Laight
2026-09-02 23:58       ` Borislav Petkov
2026-08-22 18:33 ` [PATCH v9 2/5] x86/asm, x86/boot: expose inline memcmp() Mauricio Faria de Oliveira
2026-09-06 17:01   ` Borislav Petkov
2026-09-06 18:15     ` H. Peter Anvin
2026-09-08 18:04       ` Mauricio Faria de Oliveira
2026-09-08 19:32         ` Borislav Petkov
2026-09-08 21:06           ` Mauricio Faria de Oliveira
2026-09-10  3:38             ` Borislav Petkov
2026-09-10 13:07               ` Mauricio Faria de Oliveira
2026-09-10 14:03               ` H. Peter Anvin
2026-09-08 23:16           ` H. Peter Anvin
2026-09-09  8:38             ` David Laight
2026-09-09 13:43               ` H. Peter Anvin
2026-09-09 19:28                 ` David Laight
2026-09-09 19:33                   ` H. Peter Anvin
2026-09-09 21:39                     ` David Laight
2026-09-09 23:12                       ` H. Peter Anvin
2026-09-08 17:57     ` Mauricio Faria de Oliveira
2026-08-22 18:33 ` [PATCH v9 3/5] x86/asm: group inline string functions Mauricio Faria de Oliveira
2026-08-22 18:33 ` [PATCH v9 4/5] x86/cpuid: fix unbootable VMs by really inlining memcmp() in hypervisor_cpuid_base() Mauricio Faria de Oliveira
2026-09-11  4:38   ` Borislav Petkov
2026-09-14 11:22     ` Mauricio Faria de Oliveira
2026-09-15  5:11       ` Borislav Petkov
2026-09-15  8:43         ` David Laight
2026-09-15 15:48         ` Borislav Petkov
2026-09-15 23:49           ` Mauricio Faria de Oliveira [this message]
2026-09-16  0:04             ` Borislav Petkov
2026-09-16  0:52               ` Mauricio Faria de Oliveira
2026-08-22 18:33 ` [PATCH v9 5/5] x86/pvh: fix unbootable VMs by really inlining memset() in xen_prepare_pvh() Mauricio Faria de Oliveira
2026-09-11  4:39   ` Borislav Petkov
2026-09-14 11:40     ` Mauricio Faria de Oliveira
2026-09-15  5:26       ` Borislav Petkov
2026-09-15 23:55         ` Mauricio Faria de Oliveira

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=9086138f2dcaffe30622438b7e825ae7@igalia.com \
    --to=mfo@igalia.com \
    --cc=adobriyan@gmail.com \
    --cc=boris.ostrovsky@oracle.com \
    --cc=bp@alien8.de \
    --cc=brgerst@gmail.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=hpa@zytor.com \
    --cc=jbeulich@suse.com \
    --cc=jgross@suse.com \
    --cc=kernel-dev@igalia.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=tglx@kernel.org \
    --cc=x86@kernel.org \
    --cc=xen-devel@lists.xenproject.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.