From: Catalin Marinas <catalin.marinas@arm.com>
To: Peter Collingbourne <pcc@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>,
Alexander Potapenko <glider@google.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Evgenii Stepanov <eugenis@google.com>,
linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 2/3] arm64: mte: handle tags zeroing at page allocation time
Date: Wed, 12 May 2021 13:12:46 +0100 [thread overview]
Message-ID: <20210512121245.GE14638@arm.com> (raw)
In-Reply-To: <69431af7c7d5a0688ef2aacc9e51949415df8325.1620777151.git.pcc@google.com>
On Tue, May 11, 2021 at 04:54:25PM -0700, Peter Collingbourne wrote:
> Currently, on an anonymous page fault, the kernel allocates a zeroed
> page and maps it in user space. If the mapping is tagged (PROT_MTE),
> set_pte_at() additionally clears the tags. It is, however, more
> efficient to clear the tags at the same time as zeroing the data on
> allocation. To avoid clearing the tags on any page (which may not be
> mapped as tagged), only do this if the vma flags contain VM_MTE. This
> requires introducing a new GFP flag that is used to determine whether
> to clear the tags.
>
> The DC GZVA instruction with a 0 top byte (and 0 tag) requires
> top-byte-ignore. Set the TCR_EL1.{TBI1,TBID1} bits irrespective of
> whether KASAN_HW is enabled.
>
> Signed-off-by: Peter Collingbourne <pcc@google.com>
> Co-developed-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Link: https://linux-review.googlesource.com/id/Id46dc94e30fe11474f7e54f5d65e7658dbdddb26
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
next prev parent reply other threads:[~2021-05-12 12:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 23:54 [PATCH v2 0/3] arm64: improve efficiency of setting tags for user pages Peter Collingbourne
2021-05-11 23:54 ` [PATCH v2 1/3] kasan: use separate (un)poison implementation for integrated init Peter Collingbourne
2021-05-12 12:10 ` Catalin Marinas
2021-05-12 20:08 ` Peter Collingbourne
2021-05-11 23:54 ` [PATCH v2 2/3] arm64: mte: handle tags zeroing at page allocation time Peter Collingbourne
2021-05-12 12:12 ` Catalin Marinas [this message]
2021-05-11 23:54 ` [PATCH v2 3/3] kasan: allow freed user page poisoning to be disabled with HW tags Peter Collingbourne
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