From: Paul Walmsley <pjw@kernel.org>
To: Samuel Holland <samuel.holland@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
linux-riscv@lists.infradead.org,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Deepak Gupta <debug@rivosinc.com>,
Paul Walmsley <pjw@kernel.org>,
Simon Schuster <schuster.simon@siemens-energy.com>,
Zishun Yi <vulab@iscas.ac.cn>, Zong Li <zong.li@sifive.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Revert "riscv: Reset pmm when PR_TAGGED_ADDR_ENABLE is not set"
Date: Thu, 20 Aug 2026 17:44:37 -0600 (MDT) [thread overview]
Message-ID: <866528a0-bebb-91d3-9d9d-d5f8a15b8f1c@kernel.org> (raw)
In-Reply-To: <20260820014551.1979772-1-samuel.holland@sifive.com>
On Wed, 19 Aug 2026, Samuel Holland wrote:
> This reverts commit 3033b2b1e3949274f33a140e2a97571b5a307298.
>
> The reverted patch is userspace-visible behavior change, not a bug fix.
> The two variables here (pmm and pmlen) control two independent features:
> pmm is the _hardware_ pointer masking mode that applies while executing
> in userspace. pmlen is the shift amount that the _kernel_ uses when
> untagging addresses; PMLEN_0 means no untagging occurs, so the kernel
> does not accept tagged addresses in syscall arguments.
>
> It is valid (as documented and tested by the self test) to enable
> pointer masking without enabling the tagged address ABI. This separation
> is necessary to allow userspace to create an execution environment
> similar to what the kernel supports on arm64 by default, where TBI is
> enabled but the tagged address ABI is not. (On arm64, there is no
> equivalent to PR_PMLEN_MASK because TBI is always enabled.)
>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Thanks, queued for v7.3-rc with a Fixes: tag and cc: stable.
- Paul
prev parent reply other threads:[~2026-08-20 23:44 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-20 1:45 Samuel Holland
2026-08-20 23:44 ` Paul Walmsley [this message]
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