From nobody Fri Jun 19 08:52:31 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 249CF23370F; Fri, 24 Apr 2026 13:02:23 +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=1777035745; cv=none; b=CgfPye0y/RsnJm90IoKRZRLc1jU238bbwVwLTfpXsaJIQf6p4jp8YP2TgIq+22K9PhtMvNacWjj1NE68voLNGwSK1UHVvUELN58zrD1HJG+1qPA/0Tnvd979IxehDvO+eqeG6cfwTplun8Bwz4Sr2+MfeW43179+g4/Z0EYRKRo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777035745; c=relaxed/simple; bh=orwvIT1NW1/FJElOASW5FpIR2+QTAU/sj9g+OTacCeU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Dg5ISx1Dit30KKUcSa+4ccS542iyhW79qHU+y2NHyn0lWABt+3mSB85b/Sub5R4bVwOyzZ+p+wZ5+6xtvjzqjZ2fD6X1TZ92q3OC+33/DG+s3LniiqTVC7LNp6UiQ3K9jAcZr7Lo5XK0dGP/vrN2MQmAkOwso1W75qIqNvAMuJU= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=oXcu333O; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="oXcu333O" 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 A0AC51BB0; Fri, 24 Apr 2026 06:02:17 -0700 (PDT) Received: from a080796.blr.arm.com (a080796.arm.com [10.164.21.51]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 635893F641; Fri, 24 Apr 2026 06:02:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777035743; bh=orwvIT1NW1/FJElOASW5FpIR2+QTAU/sj9g+OTacCeU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oXcu333OFMWTxoUHUEhDo+F+TLgTg4GvdV8uewai7Ub+RJP3aATmvdyWvWhhrddZB RwB4GUMp22pbW1kwZhXb+J5H7oBH9dYRAUMRhI+opuD2XsAy9XB5aApUFokoYaCOIZ cKuo7XwGH+27sthd1aAJCDbRHkZXLpLfvWwvkryk= From: Dev Jain To: arnd@arndb.de, kees@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, david@kernel.org, urezki@gmail.com Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, tglx@kernel.org, usama.anjum@arm.com, mathieu.desnoyers@efficios.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ryan Roberts , Dev Jain Subject: [PATCH v3 1/3] vmalloc: add __GFP_SKIP_KASAN support Date: Fri, 24 Apr 2026 18:31:55 +0530 Message-Id: <20260424130157.3163009-2-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260424130157.3163009-1-dev.jain@arm.com> References: <20260424130157.3163009-1-dev.jain@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Muhammad Usama Anjum 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, skip tag setting of vmalloc pages. 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. Co-developed-by: Ryan Roberts Co-developed-by: Dev Jain Signed-off-by: Muhammad Usama Anjum --- mm/vmalloc.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index b31b208f6ecb3..c94fcb2725b6b 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3939,7 +3939,7 @@ static void *__vmalloc_area_node(struct vm_struct *ar= ea, gfp_t gfp_mask, __GFP_NOFAIL | __GFP_ZERO |\ __GFP_NORETRY | __GFP_RETRY_MAYFAIL |\ GFP_NOFS | GFP_NOIO | GFP_KERNEL_ACCOUNT |\ - GFP_USER | __GFP_NOLOCKDEP) + GFP_USER | __GFP_NOLOCKDEP | __GFP_SKIP_KASAN) =20 static gfp_t vmalloc_fix_flags(gfp_t flags) { @@ -3980,6 +3980,9 @@ static gfp_t vmalloc_fix_flags(gfp_t flags) * * %__GFP_NOWARN can be used to suppress failure messages. * + * %__GFP_SKIP_KASAN can be used to skip unpoisoning of mapped pages + * (when prot=3D%PAGE_KERNEL). + * * Can not be called from interrupt nor NMI contexts. * Return: the address of the area or %NULL on failure */ @@ -3993,6 +3996,10 @@ void *__vmalloc_node_range_noprof(unsigned long size= , unsigned long align, kasan_vmalloc_flags_t kasan_flags =3D KASAN_VMALLOC_NONE; unsigned long original_align =3D align; unsigned int shift =3D PAGE_SHIFT; + bool skip_vmalloc_kasan =3D gfp_mask & __GFP_SKIP_KASAN; + + /* Don't skip metadata kasan unpoisoning */ + gfp_mask &=3D ~__GFP_SKIP_KASAN; =20 if (WARN_ON_ONCE(!size)) return NULL; @@ -4041,7 +4048,7 @@ 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()) { + if (kasan_hw_tags_enabled() && !skip_vmalloc_kasan) { /* * Modify protection bits to allow tagging. * This must be done before mapping. @@ -4054,6 +4061,12 @@ void *__vmalloc_node_range_noprof(unsigned long size= , unsigned long align, * poisoned and zeroed by kasan_unpoison_vmalloc(). */ gfp_mask |=3D __GFP_SKIP_KASAN | __GFP_SKIP_ZERO; + } else if (skip_vmalloc_kasan) { + /* + * Skip page_alloc unpoisoning physical pages backing + * VM_ALLOC mapping, as requested by caller. + */ + gfp_mask |=3D __GFP_SKIP_KASAN; } =20 /* Take note that the mapping is PAGE_KERNEL. */ @@ -4078,7 +4091,8 @@ void *__vmalloc_node_range_noprof(unsigned long size,= unsigned long align, (gfp_mask & __GFP_SKIP_ZERO)) kasan_flags |=3D KASAN_VMALLOC_INIT; /* KASAN_VMALLOC_PROT_NORMAL already set if required. */ - area->addr =3D kasan_unpoison_vmalloc(area->addr, size, kasan_flags); + if (!skip_vmalloc_kasan) + area->addr =3D kasan_unpoison_vmalloc(area->addr, size, kasan_flags); =20 /* * In this function, newly allocated vm_struct has VM_UNINITIALIZED --=20 2.34.1 From nobody Fri Jun 19 08:52:31 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DC12A23370F; Fri, 24 Apr 2026 13:02:31 +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=1777035753; cv=none; b=s6KJWLlylN51JzXi7MMhP3D/M6l4o5zl0Yic0w+qqDhUXRQzsJV46QFhOtlNvTBJJntKGzREZCQvnzQNFfjRv9A3xoCI3fz9QJO4wuPl5RvRhtuMJMJBaCaDYYRiFxCmTQ0AZXOoCerD4HPVPNMpcPBfDxqYzA1STU7Wzj6q83o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777035753; c=relaxed/simple; bh=D5X8BJo1eAEFDfHp+6/7s8DHory+FJuzYWqDtfEml9w=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=FiYgNlvc2o7kgTgZHlCWYIiUsm6kS25DlpYexGOTpBRJhrG8Q5aAXzpsk7l45U2Gk8h8vO0DfvCoM0UhhrrtSCsFbR0vVGVT+NydHZ0cy1W1W0Pt9phnh1YqtfO5uWiYYptk4E7Zfqu+TctMYu+In1yWD0aYndZ+wpCnLfzQBII= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=cnyc3BZB; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="cnyc3BZB" 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 AFDAD1BB2; Fri, 24 Apr 2026 06:02:25 -0700 (PDT) Received: from a080796.blr.arm.com (a080796.arm.com [10.164.21.51]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id B82C73F641; Fri, 24 Apr 2026 06:02:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777035751; bh=D5X8BJo1eAEFDfHp+6/7s8DHory+FJuzYWqDtfEml9w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cnyc3BZB7O71ynREGNf8/mo1oBmy01E7og062JAqbqLMBgR0ll2SwQ1Ir4hR3vbo4 uQbijEIjNYmKrks9VDj1noDm2aOzJMvl1ZBpaEEfHD+ZDaeHALsPThR7hZ8IQLtzy0 x989bATNcafg3pXnY5auXxZzSo1+thLH4tTnUHjk= From: Dev Jain To: arnd@arndb.de, kees@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, david@kernel.org, urezki@gmail.com Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, tglx@kernel.org, usama.anjum@arm.com, mathieu.desnoyers@efficios.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v3 2/3] kasan: skip HW tagging for all kernel thread stacks Date: Fri, 24 Apr 2026 18:31:56 +0530 Message-Id: <20260424130157.3163009-3-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260424130157.3163009-1-dev.jain@arm.com> References: <20260424130157.3163009-1-dev.jain@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Muhammad Usama Anjum HW-tag KASAN never checks kernel stacks because stack pointers carry the match-all tag, so setting/poisoning tags is pure overhead. - Add __GFP_SKIP_KASAN to THREADINFO_GFP so every stack allocator that uses it skips tagging (fork path plus arch users) - Add __GFP_SKIP_KASAN to GFP_VMAP_STACK for the fork-specific vmap stacks. - When reusing cached vmap stacks, skip kasan_unpoison_range() if HW tags are enabled. Software KASAN is unchanged; this only affects tag-based KASAN. Signed-off-by: Muhammad Usama Anjum --- include/linux/thread_info.h | 2 +- kernel/fork.c | 5 +++-- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index 051e429026904..307b8390fc670 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -92,7 +92,7 @@ static inline long set_restart_fn(struct restart_block *r= estart, #define THREAD_ALIGN THREAD_SIZE #endif =20 -#define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO) +#define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_SKIP_KASA= N) =20 /* * flag set/clear/test wrappers diff --git a/kernel/fork.c b/kernel/fork.c index bc2bf58b93b65..2fc3b121962cb 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -202,7 +202,7 @@ static DEFINE_PER_CPU(struct vm_struct *, cached_stacks= [NR_CACHED_STACKS]); * accounting is performed by the code assigning/releasing stacks to tasks. * We need a zeroed memory without __GFP_ACCOUNT. */ -#define GFP_VMAP_STACK (GFP_KERNEL | __GFP_ZERO) +#define GFP_VMAP_STACK (GFP_KERNEL | __GFP_ZERO | __GFP_SKIP_KASAN) =20 struct vm_stack { struct rcu_head rcu; @@ -340,7 +340,8 @@ static int alloc_thread_stack_node(struct task_struct *= tsk, int node) } =20 /* Reset stack metadata. */ - kasan_unpoison_range(vm_area->addr, THREAD_SIZE); + if (!kasan_hw_tags_enabled()) + kasan_unpoison_range(vm_area->addr, THREAD_SIZE); =20 stack =3D kasan_reset_tag(vm_area->addr); =20 --=20 2.34.1 From nobody Fri Jun 19 08:52:31 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6E0D8270545; Fri, 24 Apr 2026 13:02:40 +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=1777035762; cv=none; b=QsWjdX3rSfNvt3s1JQvYhRO+wnf08nLWXpLw/IcwG8tyxxM1bv4KsDtoA+YbUgUW63cfv7K1+cE286en+/sN8gdL9qWfa04OjP8LeH5PzLGFgc/w0HvvkwwisId51QQPRg72rYp5AP8RKUAJdP+dcLUNzkUMxmhHUEJ14O2Vdl4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777035762; c=relaxed/simple; bh=uOi1Rk96oeur1i6i7Mh3ItL6sBlXiIQnfqF3cWvMO04=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=WewWa5A3GMsRvEOcZm1iM0uadWEBhtTdfhzWxE8KiSK2ikfvqC1a6DvWlePKmFE5zWKgmApmemIvKDB+2J16xaBSyOsK0/yoW0NHo1/Q6hhttOUP6FFY4GMOPCnkbmMw1zgM5+gk0acRC5vYE1kj7tMFa5DptCFEhlEe+Ljj1U4= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=mqr3co6o; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="mqr3co6o" 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 54E8F1BB0; Fri, 24 Apr 2026 06:02:34 -0700 (PDT) Received: from a080796.blr.arm.com (a080796.arm.com [10.164.21.51]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id CAE253F641; Fri, 24 Apr 2026 06:02:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777035759; bh=uOi1Rk96oeur1i6i7Mh3ItL6sBlXiIQnfqF3cWvMO04=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mqr3co6oZde7WmeQ7llcR+8DKaBN6lEdV2rzuhYWXuiAOG/rOW4u/uqnqvMcnrVT9 WNtGghnwtzskbxD0OblP/47MNHQJQeWXs7DPMybVKZtIhHS+GFf2mzbMd1Ey9XuzMi vJHvOkfbleWtTQT86FCRDg5sXi0b91IgL4QhTL20= From: Dev Jain To: arnd@arndb.de, kees@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, david@kernel.org, urezki@gmail.com Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, tglx@kernel.org, usama.anjum@arm.com, mathieu.desnoyers@efficios.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ryan Roberts , Catalin Marinas Subject: [PATCH v3 3/3] mm: skip KASAN tagging for page-allocated page tables Date: Fri, 24 Apr 2026 18:31:57 +0530 Message-Id: <20260424130157.3163009-4-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260424130157.3163009-1-dev.jain@arm.com> References: <20260424130157.3163009-1-dev.jain@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Muhammad Usama Anjum Page tables are always accessed via the linear mapping with a match-all tag, so HW-tag KASAN never checks them. For page-allocated tables (PTEs and PGDs etc), avoid the tag setup and poisoning overhead by using __GFP_SKIP_KASAN. SLUB-backed page tables are unchanged for now. (They aren't widely used and require more SLUB related skip logic. Leave it later.) Reviewed-by: Ryan Roberts Signed-off-by: Muhammad Usama Anjum Acked-by: David Hildenbrand (Arm) Reviewed-by: Catalin Marinas --- 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 @@ =20 #ifdef CONFIG_MMU =20 -#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) =20 /** --=20 2.34.1