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h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=opc+blulF41XR2gdMM77FjNEu7ajZWNaYa0gS9RSolSJOFVKz7RXsOzo5BdWPydZx H3d72HfpHJ188WWApaaZeXaPT7fL7GAriBJ2izZYIXt/eOIKW2Ii03okk0tCtlZCno 0t4ESg+0jOqTYdL3fe+4f/92M5fvzvWBLYXP78DQ= From: Dev Jain To: akpm@linux-foundation.org, david@kernel.org, urezki@gmail.com, kees@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, arnd@arndb.de Cc: Muhammad Usama Anjum , ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, tglx@kernel.org, mathieu.desnoyers@efficios.com, linux-arch@vger.kernel.org, ryan.roberts@arm.com, catalin.marinas@arm.com, Dev Jain Subject: [PATCH v4 1/3] vmalloc: add __GFP_SKIP_KASAN support Date: Wed, 29 Apr 2026 15:57:02 +0530 Message-Id: <20260429102704.680174-2-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260429102704.680174-1-dev.jain@arm.com> References: <20260429102704.680174-1-dev.jain@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: AC2EB8000E X-Rspam-User: X-Stat-Signature: bojzg5p9smnd9qf3afst1oezkixtog9w X-HE-Tag: 1777458484-588883 X-HE-Meta: U2FsdGVkX18mKCpc8RTv8aElSOeCM3DD5+MhVpb18FT1CV2DPHA44dp4/nyfvbFePSNv1RU6SeXMGE4jDvLXABfSnMl+rzq6SctEp/QnLCb7j5f0/z8LtwHo2CrlSyowQjKNJFk0gQmRi1CvQobOHBvZ31KDnN+yCwMxX+HWL3/tCQuAzMvDg160Mo1bXr7JZOL33TFa7RDNU+rYKX6HrUvYjN/+H3dgKo7r37PG17LXSpBuUesk85hPLP4gC7AD+VVihvCXPjXJLBODKw8kEdoVWtJRAtZcKcJXQiQYlWuy45f0iRdSYem3uRM4egYPEjHTJl6rV+ZpLnrzf9STl7evt0mk0ZYYIqAO9IKyg4RALiBs6v3Mvy2PW5MtXv3SgatzNO9S0m9hEniRAz3EK9yKbsB0keKQrlkYmfTYZDxirVvpYYiqu6kgMzTPqm65OK8CrEkGKW+k9blOeMwjdqe9t8iCGfi92p88DoyGNxder+nYLSFKy18yGRYYAx2zMCKDc7sxnruGW7pQ1VLUxNM6TerDnMc7S8x/x191+YrPqvbHyZGfMVuBrKGr8RKYZiaDvqkeW4p0XJcqD1R0zWdwXvYIIA4PmvbpghqPeoe/c/E7z/AvlvhICXlrhfKgeGr9ii5OmJNqTGjZEicHCo65zOeeo03tBEdIT6IrpmuMFtlNo99ktg/CAeIRnmH/8Ud6jOEc93WKruJKZE+eL5tK6grwtd4Kvi3CoeK6JDjO33N8ZAEcqQ8/OExFRyQlDX5Sk+XkjPZUpDbpG9tAPgBUI5zRyx7Xn9EU+eIuhXH8/shEAMqGeXHtPj3AZwV2Lk/Q42P6mJZ404X/OPum0sOtBy4+bZTacGTwxnS3jVsbbtyRTTkOx1mwTQ46ftBGS+JrnXcC00Yi6B4S+E5LtJTXHqam/mSApaGQdMJhvbUPkFd4Twvf2DccAIqbJFmC3guG0REKlRdOzn3LgHO hGcDwsQa B7V8b+lY7If+X5zLkDlzDQltx+GuECgkz0AChyxJs+bUf/9G26YSQaoQLmtDx5p5eqXppZECKEWIt8ORfCXAmqF+lO3kdAUGDiyk+izGwHdh/O2rc+NN5o0Hvls/yqdch4JDze2t7FL1Q/rLxt9ck/uK5nTwDJPSp5xi7LRZ1KIwxpExJdKxhDddByusxq8Z5Au348p2PyaLN6Jnt/S9ceyhNves/jluPuSvYtFCoCuUuInXxVB9jVk0roVULj641cUR6 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 is ignored for them in the page allocator, and in vmalloc too we ignore this flag for them. This is a preparatory patch for optimizing kernel stack allocations. Signed-off-by: Muhammad Usama Anjum Co-developed-by: Ryan Roberts Signed-off-by: Ryan Roberts Co-developed-by: Dev Jain Signed-off-by: Dev Jain --- include/linux/gfp_types.h | 6 +++--- mm/vmalloc.c | 13 +++++++++---- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h index 6c75df30a281d..c2bd723c8ec62 100644 --- a/include/linux/gfp_types.h +++ b/include/linux/gfp_types.h @@ -281,9 +281,9 @@ enum { * * %__GFP_SKIP_KASAN makes KASAN skip unpoisoning on page allocation. * Used for userspace and vmalloc pages; the latter are unpoisoned by - * kasan_unpoison_vmalloc instead. For userspace pages, results in - * poisoning being skipped as well, see should_skip_kasan_poison for - * details. Only effective in HW_TAGS mode. + * kasan_unpoison_vmalloc instead. If passed to vmalloc, kasan_unpoison_vmalloc + * is skipped too. For userspace pages, results in poisoning being skipped as + * well, see should_skip_kasan_poison for details. Only effective in HW_TAGS mode. */ #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) #define __GFP_COMP ((__force gfp_t)___GFP_COMP) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index aa08651ec0df6..708ccac293cef 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3939,7 +3939,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, 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) 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=%PAGE_KERNEL). + * * Can not be called from interrupt nor NMI contexts. * Return: the address of the area or %NULL on failure */ @@ -3993,6 +3996,7 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, kasan_vmalloc_flags_t kasan_flags = KASAN_VMALLOC_NONE; unsigned long original_align = align; unsigned int shift = PAGE_SHIFT; + bool skip_vmalloc_kasan = kasan_hw_tags_enabled() && (gfp_mask & __GFP_SKIP_KASAN); if (WARN_ON_ONCE(!size)) return NULL; @@ -4023,7 +4027,7 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, again: area = __get_vm_area_node(size, align, shift, VM_ALLOC | VM_UNINITIALIZED | vm_flags, start, end, node, - gfp_mask, caller); + gfp_mask & ~__GFP_SKIP_KASAN, caller); if (!area) { bool nofail = gfp_mask & __GFP_NOFAIL; warn_alloc(gfp_mask, NULL, @@ -4041,7 +4045,7 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, * kasan_unpoison_vmalloc(). */ if (pgprot_val(prot) == 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. @@ -4078,7 +4082,8 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, (gfp_mask & __GFP_SKIP_ZERO)) kasan_flags |= KASAN_VMALLOC_INIT; /* KASAN_VMALLOC_PROT_NORMAL already set if required. */ - area->addr = kasan_unpoison_vmalloc(area->addr, size, kasan_flags); + if (!skip_vmalloc_kasan) + area->addr = kasan_unpoison_vmalloc(area->addr, size, kasan_flags); /* * In this function, newly allocated vm_struct has VM_UNINITIALIZED -- 2.34.1