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bh=0QB+Qvxjjp0fPU4pPP754f+dTc32bLiJD+Cyf8FT9Y8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AgsKn4Dxtc+zw54Fg3JARa6pKd6EWx9WJ4N4tIieLoiO0Yh9LcDjFwHvK/lNO6zbk 1NbhPkF0DRY2QP4bp1+HDQmSK21srsJJdMhaaHcvYnXNPCQ2C+uYwSBue7h1A8ZO1c HR4bYnQBmkZ5GexDoMfV0gabeltW9XYjiNMbL2/g= Date: Wed, 29 Apr 2026 15:43:23 +0100 From: Catalin Marinas To: Dev Jain Cc: 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, 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 Subject: Re: [PATCH v4 2/3] kasan: skip HW tagging for all kernel thread stacks Message-ID: References: <20260429102704.680174-1-dev.jain@arm.com> <20260429102704.680174-3-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260429102704.680174-3-dev.jain@arm.com> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 992F81C0010 X-Stat-Signature: hb3aanep61gsmecchd77zbc5jcdz1gdc X-Rspam-User: X-HE-Tag: 1777473816-53800 X-HE-Meta: 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 v+uHWUDl qLapkGG6HamWOLFjZhRoDDt5VJjzNn2ABfMTdyzSB+f63fPCl154IFLQBIKbpTlJKYQhNE2WsHvcPLsMTSiKq+BprGMbzfbg4taVuiVmdiTVEif9b1p1FRaMObRUF95byksP2xoChPO9IQxO1EkMkPFl/YTT1OFmSaSMjfyqbY5IUljfcJve9hX5OHOwPupW4YNjM8bB2uhfDtZrKCac4OJGEVZSUINVrHWi8X0vpxaR4l7+IOoPjnCFwQYeYRSCT6WPFTLuwCrW1Q42S92jvdJwuWjaVfk7bl0G/dzIW/YR3LkN4vo8PsjvUl2+kyVKnkw8mtbMABNtHpd8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 29, 2026 at 03:57:03PM +0530, Dev Jain wrote: > 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 > Signed-off-by: Dev Jain Reviewed-by: Catalin Marinas