From: Usama Arif <usama.arif@linux.dev>
To: Rik van Riel <riel@surriel.com>
Cc: Usama Arif <usama.arif@linux.dev>,
linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org,
"Thomas Gleixner" <tglx@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Dmitry Ilvokhin" <d@ilvokhin.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"David Hildenbrand" <david@kernel.org>,
"Lorenzo Stoakes" <ljs@kernel.org>,
"Liam R. Howlett" <liam@infradead.org>,
"Vlastimil Babka" <vbabka@kernel.org>,
"Suren Baghdasaryan" <surenb@google.com>
Subject: Re: [PATCH 1/3] x86/mm: use READ_ONCE/WRITE_ONCE for mm->context.untag_mask
Date: Thu, 18 Jun 2026 09:40:42 -0700 [thread overview]
Message-ID: <20260618164043.784764-1-usama.arif@linux.dev> (raw)
In-Reply-To: <20260616190300.1509639-2-riel@surriel.com>
On Tue, 16 Jun 2026 15:02:58 -0400 Rik van Riel <riel@surriel.com> wrote:
> mm->context.untag_mask is written once, when LAM is enabled
> (mm_enable_lam(), under mmap_write_lock and while the process is still
> single-threaded), and is otherwise stable and never reverted.
> untagged_addr_remote() reads it for a remote mm, and the new
> untagged_addr_remote_unlocked() (used by the per-VMA-lock
> access_remote_vm() fast path) reads it without the mmap lock.
>
> The field is a single aligned word and cannot tear, but annotate the
> reads and writes with READ_ONCE()/WRITE_ONCE() to make the lockless
> access explicit and keep the compiler from reloading or tearing it.
>
> No functional change.
>
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Rik van Riel <riel@surriel.com>
> ---
> arch/x86/include/asm/mmu_context.h | 6 +++---
> arch/x86/include/asm/uaccess_64.h | 2 +-
> arch/x86/kernel/process_64.c | 2 +-
> 3 files changed, 5 insertions(+), 5 deletions(-)
>
Acked-by: Usama Arif <usama.arif@linux.dev>
next prev parent reply other threads:[~2026-06-18 16:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-16 19:02 [PATCH 0/3] mm: __access_remote_vm with per-VMA lock Rik van Riel
2026-06-16 19:02 ` [PATCH 1/3] x86/mm: use READ_ONCE/WRITE_ONCE for mm->context.untag_mask Rik van Riel
2026-06-18 16:40 ` Usama Arif [this message]
2026-06-16 19:02 ` [PATCH 2/3] mm/pagewalk: let folio_walk_start() run under the per-VMA lock Rik van Riel
2026-06-16 19:03 ` [PATCH 3/3] mm: read remote memory without the mmap lock where possible Rik van Riel
2026-06-17 6:19 ` Suren Baghdasaryan
2026-06-18 17:01 ` Usama Arif
2026-06-18 17:07 ` David Hildenbrand (Arm)
2026-06-18 17:22 ` Usama Arif
2026-06-17 1:10 ` [PATCH 0/3] mm: __access_remote_vm with per-VMA lock Suren Baghdasaryan
2026-06-17 9:42 ` David Hildenbrand (Arm)
2026-06-17 13:33 ` Suren Baghdasaryan
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