From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0755C54F32 for ; Wed, 28 Aug 2024 12:36:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4A9466B0092; Wed, 28 Aug 2024 08:36:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 459F26B0095; Wed, 28 Aug 2024 08:36:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 349246B0096; Wed, 28 Aug 2024 08:36:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 1C2B36B0092 for ; Wed, 28 Aug 2024 08:36:55 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 91F8E81F5A for ; Wed, 28 Aug 2024 12:36:54 +0000 (UTC) X-FDA: 82501603548.29.05977C0 Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by imf03.hostedemail.com (Postfix) with ESMTP id 88B372000C for ; Wed, 28 Aug 2024 12:36:51 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf03.hostedemail.com: domain of segher@kernel.crashing.org designates 63.228.1.57 as permitted sender) smtp.mailfrom=segher@kernel.crashing.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724848541; a=rsa-sha256; cv=none; b=ArokmqTtPfqZmwBrWUccno6L9qTZTAV+09phSgCqeyDyI7icjDzmMuTXrM/ydr9aPh1BB0 J8tA20tI149he23raMmHhrtS3tc6PCy/amiZnpq5muBqZBD+hXFx2A+T/Y/hvZKotHR3DZ 5XtRuzSMDF1AT+nACQD57gg2lKe/q1s= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf03.hostedemail.com: domain of segher@kernel.crashing.org designates 63.228.1.57 as permitted sender) smtp.mailfrom=segher@kernel.crashing.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724848541; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JkYTmJmrONNGhzJRE1nYc3r8lueDSK8+AxPwwEGRl0E=; b=UgFL4T6UHM7SVe+VA3s8eyEmkYzFpHde8FDTM5uMlkdM7GDIcXhRiKAoi+zA+ARuzzZIXj 6GzplsdIL60jZj5kdIYVIClCy896y7+Kg+b7ZxjGWCYNSicGOKgLkDYUYkPbEBSl4x7B/q YEHoRoYwz1BRJ9Nq11AvXQFOJDxYr8U= Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 47SCXFAC030999; Wed, 28 Aug 2024 07:33:15 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 47SCXDte030998; Wed, 28 Aug 2024 07:33:13 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Wed, 28 Aug 2024 07:33:13 -0500 From: Segher Boessenkool To: "Jason A. Donenfeld" Cc: Eric Biggers , Christophe Leroy , Michael Ellerman , Nicholas Piggin , Naveen N Rao , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , "Theodore Ts'o" , Arnd Bergmann , Andrew Morton , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Vincenzo Frascino , Shuah Khan , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v2 05/17] vdso: Avoid call to memset() by getrandom Message-ID: <20240828123313.GD29862@gate.crashing.org> References: <5deb67090b214f0e6eae96b7c406546d1a16f89b.1724309198.git.christophe.leroy@csgroup.eu> <20240827180819.GB2049@sol.localdomain> <20240827225330.GC29862@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 88B372000C X-Stat-Signature: mhxgejz1ko8z1o49p8nmuccxj9psrzbk X-Rspam-User: X-HE-Tag: 1724848611-182142 X-HE-Meta: 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 CaSB1jLR 8WWNMiuCm8nkPLCf//hPCqnQ/mFp6LzdIudz9iUPK/DsDEAXVcP3iUaaMUl5Av7POAvCC3TGPyVW0tspahsABNt+OSKWXxzh/jC0d0GQd4lY4urw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 28, 2024 at 01:18:34PM +0200, Jason A. Donenfeld wrote: > On Tue, Aug 27, 2024 at 05:53:30PM -0500, Segher Boessenkool wrote: > > On Tue, Aug 27, 2024 at 11:08:19AM -0700, Eric Biggers wrote: > > > > + for (i = 0; i < ARRAY_SIZE(params->reserved); i++) > > > > + params->reserved[i] = 0; This is a loop. With -ftree-loop-distribute-patterns, the default at -O2, this is optimised to memset(params->reserved, 0, ...); (which is perfectly fine, since memset is required to be there even for freestanding environments, this is documented!) > > -fno-tree-loop-distribute-patterns . But, as always, read up on it, see > > what it actually does (and how it avoids your problem, and mostly: learn > > what the actual problem *was*!) > > This might help with various loops, but it doesn't help with the matter > that this patch fixes, which is struct initialization. I just tried it > with the arm64 patch to no avail. It very much *does* help. Try harder? Maybe you typoed? Segher