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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 38B08108E1FD for ; Thu, 19 Mar 2026 12:09:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8C82A6B049A; Thu, 19 Mar 2026 08:09:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 878EF6B049C; Thu, 19 Mar 2026 08:09:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 78E5D6B049D; Thu, 19 Mar 2026 08:09:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 6A3716B049A for ; Thu, 19 Mar 2026 08:09:43 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 00D2F1A0543 for ; Thu, 19 Mar 2026 12:09:42 +0000 (UTC) X-FDA: 84562693446.21.5709AD3 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf12.hostedemail.com (Postfix) with ESMTP id 23E2040006 for ; Thu, 19 Mar 2026 12:09:40 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=none; spf=pass (imf12.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1773922181; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IJ4WIStSSV7fmI+rD+2HcG1uK56zJNOoF3Q0UnlUfx4=; b=vUTtagvOEY3dPKR20UdQ68NXqT5sqRcQhT5/gIRrpO6YvYrvHvJgU5ScLVN8zQLMoAsy+N 0+OoEsdzLFeEmtuB/8LAM34aoHzRTaCbFXPvLjbx6VjdLHzCIlTwF3NGZxyy/5CbY/Vy8w C2Y5I6S4sRa+Cb7DaI5AESfBzrdgyWE= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=none; spf=pass (imf12.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773922181; a=rsa-sha256; cv=none; b=SDEDYEKteyWxU0eG2LuY6Qk8Rf5ZC2S88JefDf4fYXvuB1G6QqVZPUNCBBA9f+V1VX7xy2 YF1qFOjY700eGcEdE0abQ4aKrPERB8awbZXT7y64i9jTXpAifvDLUfqncBIc+vUlkI10+Z ECUxvbiEo1MB2N3qzlY1/uQF3wUikFU= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 431231BD0; Thu, 19 Mar 2026 05:09:34 -0700 (PDT) Received: from [10.57.85.34] (unknown [10.57.85.34]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 648373F778; Thu, 19 Mar 2026 05:09:36 -0700 (PDT) Message-ID: <75705c3d-2654-47cf-8fd3-8343136715fa@arm.com> Date: Thu, 19 Mar 2026 12:09:34 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] mm: SKIP KASAN for page table allocations Content-Language: en-GB To: Muhammad Usama Anjum , Arnd Bergmann , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Kees Cook , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Uladzislau Rezki , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrey Konovalov , Marco Elver , Vincenzo Frascino , Peter Collingbourne , Catalin Marinas , Will Deacon , david.hildenbrand@arm.com References: <20260319114952.3241359-1-usama.anjum@arm.com> <20260319114952.3241359-4-usama.anjum@arm.com> From: Ryan Roberts In-Reply-To: <20260319114952.3241359-4-usama.anjum@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: notjbybbt4sobatxgt39fyoe1pjhtwq1 X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 23E2040006 X-HE-Tag: 1773922180-150920 X-HE-Meta: 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 gcmET4WK 1wGIts+n+kV1CJ2WcXU4gbhUUClz0AnoIVIU0Aje1Iai8oL9TRZB2VDvWCtWa7BGd2gog/AC6WCN4HbJv3PrlN1nU3iX6Dq2NmfosLY56NmYIYZvvpaNoTL/lqL4TNq6yUd1G8ukc9hAXz1YhOSISNud/yRJvBt/Ny6c9CHDbw5d8ZhA8nOPsUvFMjaC/B7+JHtjuZpuO0mYTv7A= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 19/03/2026 11:49, Muhammad Usama Anjum wrote: > Page tables are always accessed via __va(phys) / phys_to_virt(phys). > With a match-all tag in the pointer, MTE never checks memory tags on > access. Therefore: KASAN HW tags are set during page table allocation > but never checked during use. KASAN poisoning on free provides no > value for these pages as well. Its pure overhead - both at allocation > time and free time. Hence, skip the tag setting for all page tables. > > Signed-off-by: Muhammad Usama Anjum Reviewed-by: Ryan Roberts > --- > include/asm-generic/pgalloc.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h > index 57137d3ac1592..051aa1331051c 100644 > --- a/include/asm-generic/pgalloc.h > +++ b/include/asm-generic/pgalloc.h > @@ -4,7 +4,7 @@ > > #ifdef CONFIG_MMU > > -#define GFP_PGTABLE_KERNEL (GFP_KERNEL | __GFP_ZERO) > +#define GFP_PGTABLE_KERNEL (GFP_KERNEL | __GFP_ZERO | __GFP_SKIP_KASAN) > #define GFP_PGTABLE_USER (GFP_PGTABLE_KERNEL | __GFP_ACCOUNT) > > /**