linux-kernel - Re: [PATCH v4 03/16] x86/alternatives: Disable LASS when patching kernel alternatives

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: <20240711012333.GAZo80FU30_x77otP4@fat_crate.local>
Date: Thu, 11 Jul 2024 03:23:33 +0200
From: Borislav Petkov <bp@...en8.de>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Xiongwei Song <xiongwei.song@...driver.com>,
	Xin Li <xin3.li@...el.com>, "Mike Rapoport (IBM)" <rppt@...nel.org>,
	Brijesh Singh <brijesh.singh@....com>,
	Michael Roth <michael.roth@....com>,
	Tony Luck <tony.luck@...el.com>, Alexey Kardashevskiy <aik@....com>,
	Jonathan Corbet <corbet@....net>,
	Sohil Mehta <sohil.mehta@...el.com>, Ingo Molnar <mingo@...nel.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Sandipan Das <sandipan.das@....com>,
	Breno Leitao <leitao@...ian.org>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Yian Chen <yian.chen@...el.com>,
	Alexei Starovoitov <ast@...nel.org>, Hou Tao <houtao1@...wei.com>,
	Juergen Gross <jgross@...e.com>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Kees Cook <kees@...nel.org>, Eric Biggers <ebiggers@...gle.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Yuntao Wang <ytcoode@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Tejun Heo <tj@...nel.org>, Changbin Du <changbin.du@...wei.com>,
	Huang Shijie <shijie@...amperecomputing.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org
Subject: Re: [PATCH v4 03/16] x86/alternatives: Disable LASS when patching
 kernel alternatives

On Thu, Jul 11, 2024 at 01:33:23AM +0300, Kirill A. Shutemov wrote:
> Hm. Do we have text_poke() in hot path?
> 
> Even if we do, I doubt flipping AC flag would make any performance
> difference in context of all locking and TLB flushing we do in this
> codepath.

$ dmesg | grep text_poke | wc -l
237

In a silly guest.

And regardless, we don't do unnecessary toggling of rFLAGS.AC.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette