From: Michael Ellerman <mpe@ellerman•id.au>
To: Arnd Bergmann <arnd@arndb•de>,
Charlie Jenkins <charlie@rivosinc•com>,
Lorenzo Stoakes <lorenzo.stoakes@oracle•com>
Cc: Richard Henderson <richard.henderson@linaro•org>,
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Subject: Re: [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47 bits
Date: Wed, 11 Sep 2024 23:50:05 +1000 [thread overview]
Message-ID: <87zfoeqoz6.fsf@mail.lhotse> (raw)
In-Reply-To: <89d21669-8daa-4225-b6d2-33d439ebd746@app.fastmail.com>
"Arnd Bergmann" <arnd@arndb•de> writes:
> On Mon, Sep 9, 2024, at 23:22, Charlie Jenkins wrote:
>> On Fri, Sep 06, 2024 at 10:52:34AM +0100, Lorenzo Stoakes wrote:
>>> On Fri, Sep 06, 2024 at 09:14:08AM GMT, Arnd Bergmann wrote:
>>> The intent is to optionally be able to run a process that keeps higher bits
>>> free for tagging and to be sure no memory mapping in the process will
>>> clobber these (correct me if I'm wrong Charlie! :)
...
> Let's see what the other architectures do and then come up with
> a way that fixes the pointer tagging case first on those that are
> broken. We can see if there needs to be an extra flag after that.
> Here is what I found:
>
> - x86_64 uses DEFAULT_MAP_WINDOW of BIT(47), uses a 57 bit
> address space when an addr hint is passed.
> - arm64 uses DEFAULT_MAP_WINDOW of BIT(47) or BIT(48), returns
> higher 52-bit addresses when either a hint is passed or
> CONFIG_EXPERT and CONFIG_ARM64_FORCE_52BIT is set (this
> is a debugging option)
> - ppc64 uses a DEFAULT_MAP_WINDOW of BIT(47) or BIT(48),
> returns 52 bit address when an addr hint is passed
It's 46 or 47 depending on PAGE_SIZE (4K or 64K):
$ git grep "define DEFAULT_MAP_WINDOW_USER64" arch/powerpc/include/asm/task_size_64.h
arch/powerpc/include/asm/task_size_64.h:#define DEFAULT_MAP_WINDOW_USER64 TASK_SIZE_128TB
arch/powerpc/include/asm/task_size_64.h:#define DEFAULT_MAP_WINDOW_USER64 TASK_SIZE_64TB
cheers
next prev parent reply other threads:[~2024-09-11 13:50 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-05 21:15 [PATCH RFC v3 0/2] mm: Introduce ADDR_LIMIT_47BIT personality flag Charlie Jenkins
2024-09-05 21:15 ` [PATCH RFC v3 1/2] mm: Add personality flag to limit address to 47 bits Charlie Jenkins
2024-09-06 6:59 ` Michael Ellerman
2024-09-09 19:07 ` Charlie Jenkins
2024-09-10 9:20 ` Christophe Leroy
2024-09-10 12:43 ` Geert Uytterhoeven
2024-09-11 13:38 ` Michael Ellerman
2024-09-12 6:20 ` Charlie Jenkins
2024-09-20 5:10 ` Michael Ellerman
2024-09-11 13:37 ` Michael Ellerman
2024-09-06 7:17 ` Arnd Bergmann
2024-09-06 8:02 ` Lorenzo Stoakes
2024-09-06 8:14 ` Lorenzo Stoakes
2024-09-06 9:14 ` Arnd Bergmann
2024-09-06 9:52 ` Lorenzo Stoakes
2024-09-09 23:22 ` Charlie Jenkins
2024-09-10 9:13 ` Arnd Bergmann
2024-09-10 23:29 ` Charlie Jenkins
2024-09-11 13:50 ` Michael Ellerman [this message]
2024-09-06 9:14 ` Guo Ren
2024-09-06 9:55 ` Arnd Bergmann
2024-09-06 11:43 ` Catalin Marinas
2024-09-10 19:08 ` Liam R. Howlett
2024-09-11 0:45 ` Charlie Jenkins
2024-09-11 7:25 ` Arnd Bergmann
2024-09-12 6:06 ` Charlie Jenkins
2024-09-11 18:21 ` Catalin Marinas
2024-09-12 6:18 ` Charlie Jenkins
2024-09-12 10:53 ` Catalin Marinas
2024-09-12 21:15 ` Charlie Jenkins
2024-09-13 10:08 ` Catalin Marinas
2024-09-13 10:21 ` Catalin Marinas
2024-09-13 20:15 ` Charlie Jenkins
2024-09-13 7:41 ` Lorenzo Stoakes
2024-09-13 21:04 ` Charlie Jenkins
2024-10-02 14:26 ` Palmer Dabbelt
2024-09-05 21:15 ` [PATCH RFC v3 2/2] selftests/mm: Create ADDR_LIMIT_47BIT test Charlie Jenkins
2024-09-06 6:08 ` [PATCH RFC v3 0/2] mm: Introduce ADDR_LIMIT_47BIT personality flag Guo Ren
2024-09-06 6:19 ` John Paul Adrian Glaubitz
2024-09-08 11:26 ` Jiaxun Yang
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