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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 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> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: md61yg8cq5rxpbnygwk6ftxx7rgewmrj X-Rspamd-Queue-Id: 3629E100004 X-Rspamd-Server: rspam03 X-HE-Tag: 1773921010-595039 X-HE-Meta: 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 RJs20vfc YFNZDm1MEjeUth3X3ccWl0NpTaN8+4XdULAaO5hH1kOIe3p9MRq7qWUyBs63aePyzi94TNz05j4FonqcKCCDn4mhNZc92ig4my2tSwOaEK51JIMCJbh68s/391Qb2S1CdbnnSbegqjwrEO4Lu78RixzGT+ehYtGmj5Q1wqtdSJ81F6FxY4Q7Pj9N+umiC4mnYwAKTrUzDNuD69+GCPSdRCj9SanCZwCXRKjJ6LsNgKMfuNxYWxjFQzGFaTlFjCWh0RgToQM7jejmww5QS9vJrNw5/Nw== 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 --- 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) == pgprot_val(PAGE_KERNEL)) { - if (kasan_hw_tags_enabled()) { + bool skip_kasan = 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, } /* 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