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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 57D9D180024 X-Stat-Signature: s7p5qugmmstdfyo8btbk9z7yizc5y75p X-Rspam-User: X-HE-Tag: 1777035744-39979 X-HE-Meta: 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 eCH0bAE0 3JMu7sZsKOa6OJk0VQJkvTEB4QU0/Rn8q5p/11VGtjOekRdPahzZh2XDaUKxZuqNJOQVGfgZ+JZ+Qy8RE+gVUGFcLPMfkPBKD5fUbnve+vS8sUumnRExUnkZ+Bt4PDeaCq18U6jfmCUKvbK5cqdkPinj1dFOL3fsDafUTE0PahNVRpgTzHsGr2Y/HA3cXvCaYBkIvRS44Y44OnBrujhSC5WSdKsaticWD5s1PL4GBUVDaNOu6PzwHSGLnJwyz/LA2Y5ZHqRSjSgHcp0a2Y16VZTklPHgAQGsX1zJgyZt9e4EZRKEWTHNp5pfsHxYT2HMJEbTZcbvOO8Mxct0= 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 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 *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 +3996,10 @@ 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 = gfp_mask & __GFP_SKIP_KASAN; + + /* Don't skip metadata kasan unpoisoning */ + gfp_mask &= ~__GFP_SKIP_KASAN; 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) == 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 |= __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 |= __GFP_SKIP_KASAN; } /* 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 |= 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