From nobody Mon Apr 6 12:17:08 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9F1F13CBE77; Thu, 19 Mar 2026 11:50:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773921011; cv=none; b=N6WjyMw1SCLQ1ePizXTkT/WGr4ijppX0WB1azTpp6NyId470F5BKXIWRVg5MBpYVy0aD0ZDXP/X18/dLZPvB1jSOlg0eeHibPkkE4qenZXXm9XqJeF7fudEubbBKRSgR7XS4U+4J6PsHW/TRJOFY3RMlU+tFxbGsw2l5ivl7Q5A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773921011; c=relaxed/simple; bh=1A19svTFNimiMX0p7MePOMchlMQE04htLe+BZ1KV7so=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UnnEOTR10AtjdbpMIketAh/JGXSmZxooY7eGGm9eMEzlBcdI0ZtZT66s9tryQznKWyli0u3ZfOHjL/CQMBfPMs2lxOiyjD44lWs2nqfgevpWAQpbsEAI1ZT6NCdfwWb50V1UqFKwFDYe74XeMp4RmX1h9Sz0r65t8vwYp9esvtk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 E2FDC1BD0; Thu, 19 Mar 2026 04:50:02 -0700 (PDT) Received: from e142334-100.cambridge.arm.com (e142334-100.cambridge.arm.com [10.1.194.63]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id B3FE63F778; Thu, 19 Mar 2026 04:50:04 -0700 (PDT) From: Muhammad Usama Anjum To: 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 , Ryan.Roberts@arm.com, david.hildenbrand@arm.com Cc: Muhammad Usama Anjum Subject: [PATCH 1/3] vmalloc: add __GFP_SKIP_KASAN support Date: Thu, 19 Mar 2026 11:49:44 +0000 Message-ID: <20260319114952.3241359-2-usama.anjum@arm.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260319114952.3241359-1-usama.anjum@arm.com> References: <20260319114952.3241359-1-usama.anjum@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable For allocations that will be accessed only with match-all pointers (e.g., kernel stacks), setting tags is wasted work. If the caller already set __GFP_SKIP_KASAN, don=E2=80=99t skip zeroing the pages and don=E2=80=99t set KASAN_VMALLOC_PROT_NORMAL so kasan_unpoison_vmalloc() returns early without tagging. Before this patch, __GFP_SKIP_KASAN wasn't being used with vmalloc APIs. So it wasn't being checked. Now its being checked and acted upon. Other KASAN modes are unchanged because __GFP_SKIP_KASAN isn't defined there. This is a preparatory patch for optimizing kernel stack allocations. Signed-off-by: Muhammad Usama Anjum --- mm/vmalloc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index c607307c657a6..1baa602a0b9bb 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4041,7 +4041,10 @@ void *__vmalloc_node_range_noprof(unsigned long size= , unsigned long align, * kasan_unpoison_vmalloc(). */ if (pgprot_val(prot) =3D=3D pgprot_val(PAGE_KERNEL)) { - if (kasan_hw_tags_enabled()) { + bool skip_kasan =3D kasan_hw_tags_enabled() && + (gfp_mask & __GFP_SKIP_KASAN); + + if (kasan_hw_tags_enabled() && !skip_kasan) { /* * Modify protection bits to allow tagging. * This must be done before mapping. @@ -4057,7 +4060,8 @@ void *__vmalloc_node_range_noprof(unsigned long size,= unsigned long align, } =20 /* Take note that the mapping is PAGE_KERNEL. */ - kasan_flags |=3D KASAN_VMALLOC_PROT_NORMAL; + if (!skip_kasan) + kasan_flags |=3D KASAN_VMALLOC_PROT_NORMAL; } =20 /* Allocate physical pages and map them into vmalloc space. */ --=20 2.47.3