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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 v2 1/3] vmalloc: add __GFP_SKIP_KASAN support Date: Tue, 24 Mar 2026 13:26:27 +0000 Message-ID: <20260324132631.482520-2-usama.anjum@arm.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260324132631.482520-1-usama.anjum@arm.com> References: <20260324132631.482520-1-usama.anjum@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: jhxdq6585npgktgqz3dm33aonqikrw3g X-Rspamd-Queue-Id: 57ED440017 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1774358814-606287 X-HE-Meta: U2FsdGVkX1/SNzVWFh/WgzgLV4K+8BWL/QPNiwuM1FlQ15PxZuYmXf9LyBa5DcluuvSSzuAghjHW/RV3HotGDRq7qRLs+yoN7D57Ye+Mp8NJjV5mC4skV+EaNb9sNblFn/t6+YNfMldoJsLZozkdgCop2iIc2vkHrpcW3NNbwMo51UGvBjXXqg1WslHMXL1kFZyEPwutnofI0rYOFEAIznP8Z5mW6sBn4a+VXrMXLDzhBKzxOtjdtlXnj0FoCMpeYjqt4dxikD+84VNgKQtntJKfUAEsMyUc0SaGZgGxVy49FZQ/1aDkwqRaRS5JWaYY9jLEpib7aAyR1SRrEqc4kp8r34tUKo28LM2Ki+wTqscXR+SpI9COYmLaUcpa9qe0tqH3vUaVMefhbbgSq13gQ6oS/+2WLyPf37BfkCDqPRoUbnvVHffcepGs7Y7XYQluyRnp2LxOhjfS7icVt9miP2RsFpo5fdd424Q6s4D1NHDd/+3w4Navz8L6/XakE+xgHb0SQZwVSceZPVLz3CwtVXyJ3V7lML/pyrCx6PyIMBhbYRw5OS/mP+aphZQ2NBrUS/bgLcOD/1mq3whMgjIZQETVLb/qyTQV8usdZZTNtNpxGypemmqmQuJf5i1Ozs2ILkjZDkTOBONeKj62VRpabTEYBHR+f4IYkpU3CyfHwkSR90zQk3aWIL2VLsbiRL69xHmtsb1ahMhONRwo93NASBfUEWsYKuWvuQS6bMIL1BT6vHu7V9F2JyGz6ftZTrNsOS21BkPp8JE7GyrLdSJoPZOFaV0Rnr5+RedCK3uSNtc3F1dN893QT9iXrkwRl3FFte/EF7GDL55DO4JLqAALihFrRGxjPcUScOzjDpcB2XrcoV2AqwEr998xFuw5CJAO5mGNO12d9lRkgdWvfJ/uXjF/3Ir4p2/+0WOsj+CuxRSwH9vXPl3EyTFteUZ9HzMAqU1TJwoJokYJP2mQvYU x6XziBgF fREGfq7jOvJtxw3HdySpR3kv66G7O58EZTWVqun967teM6vtWhZaR/m7pdH0z9G47wYdiNLPlLlEMB66ffJnsvjRdVf3grPlis+1fFVk7KqHwovelkX1xYxOvE5flL23hxEcGPhcj3QTaf5Qi/T5S5p51IZN01YPGtejtWx6M6CRovd+sOy6iQlDqYpNeCOpaQvjEqJs0QAICcaR1VB75+9gu22BciRD/z1o6BVRogIPupAO9hFvcjO30mNiVAHKu4LxwBrug0dNq73Q5lCMMLmB9szugHtHdlG3dnDMdQKuEd387pn4E4hFkFJHoXyPHrx920bd0KwcY4t0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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’t skip zeroing the pages and don’t 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 --- Changes since v1: - Simplify skip conditions based on the fact that __GFP_SKIP_KASAN is zero in non-hw-tags mode. - Add __GFP_SKIP_KASAN to GFP_VMALLOC_SUPPORTED list of flags --- mm/vmalloc.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index c607307c657a6..69ae205effb46 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 +3980,8 @@ 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 poisoning + * * Can not be called from interrupt nor NMI contexts. * Return: the address of the area or %NULL on failure */ @@ -4041,7 +4043,9 @@ 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()) { + bool skip_kasan = 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 +4061,8 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align, } /* Take note that the mapping is PAGE_KERNEL. */ - kasan_flags |= KASAN_VMALLOC_PROT_NORMAL; + if (!skip_kasan) + kasan_flags |= KASAN_VMALLOC_PROT_NORMAL; } /* Allocate physical pages and map them into vmalloc space. */ -- 2.47.3