From: "Michael S. Tsirkin" <mst@redhat.com>
To: Eugenio Perez Martin <eperezma@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>,
Laurent Vivier <lvivier@redhat.com>,
virtualization@lists.linux.dev,
Maxime Coquelin <mcoqueli@redhat.com>, Cindy Lu <lulu@redhat.com>,
linux-kernel@vger.kernel.org,
Yongji Xie <xieyongji@bytedance.com>,
Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
Stefano Garzarella <sgarzare@redhat.com>
Subject: Re: [PATCH v9 5/6] vduse: add vq group asid support
Date: Mon, 17 Nov 2025 05:50:19 -0500 [thread overview]
Message-ID: <20251117054850-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAJaqyWex0rE+KO-UE_qxqkG3RWWP4ntNy+9Nzvb+CZ+auR3mVw@mail.gmail.com>
On Fri, Nov 14, 2025 at 12:25:03PM +0100, Eugenio Perez Martin wrote:
> RCU is protecting that the address space pointer of the vq group is
> not modified concurrently with the access. Ideally, this should be a
> full lock, but just making sure that all accesses from the reader are
> coherent is enough. Userspace should expect nothing if it uses the map
> and modifies the vq group ASID at the same time anyway, but the kernel
> needs to be sure that it does not see intermediate states. TBH, we
> could move to a READ_ONCE / WRITE_ONCE, would that be more clear?
generally rcu itself does not need ONCE macros.
these are for funky lockless things, and rcu can be
seen as a kind of lock, after all.
--
MST
next prev parent reply other threads:[~2025-11-17 10:50 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-13 11:55 [PATCH v9 0/6] Add multiple address spaces support to VDUSE Eugenio Pérez
2025-11-13 11:55 ` [PATCH v9 1/6] vduse: add v1 API definition Eugenio Pérez
2025-11-13 11:55 ` [PATCH v9 2/6] vduse: add vq group support Eugenio Pérez
2025-11-13 11:55 ` [PATCH v9 3/6] vduse: return internal vq group struct as map token Eugenio Pérez
2025-11-13 11:55 ` [PATCH v9 4/6] vduse: refactor vdpa_dev_add for goto err handling Eugenio Pérez
2025-11-13 11:55 ` [PATCH v9 5/6] vduse: add vq group asid support Eugenio Pérez
2025-11-14 0:55 ` Jason Wang
2025-11-14 11:25 ` Eugenio Perez Martin
2025-11-17 4:23 ` Jason Wang
2025-11-17 12:15 ` Eugenio Perez Martin
2025-11-19 2:38 ` Jason Wang
2025-11-19 9:26 ` Eugenio Perez Martin
2025-11-19 9:32 ` Michael S. Tsirkin
2025-11-19 10:38 ` Eugenio Perez Martin
2025-11-19 12:29 ` Michael S. Tsirkin
2025-11-20 1:37 ` Jason Wang
2025-12-03 7:57 ` Eugenio Perez Martin
2025-12-04 2:15 ` Jason Wang
2025-12-04 8:32 ` Eugenio Perez Martin
2025-12-05 1:51 ` Jason Wang
2025-12-05 15:30 ` Eugenio Perez Martin
2025-12-08 2:58 ` Jason Wang
2025-11-17 10:50 ` Michael S. Tsirkin [this message]
2025-11-17 12:16 ` Eugenio Perez Martin
2025-11-14 6:46 ` kernel test robot
2025-11-14 6:47 ` kernel test robot
2025-11-17 3:10 ` 谢永吉
2025-11-17 9:08 ` Eugenio Perez Martin
2025-11-13 11:55 ` [PATCH v9 6/6] vduse: bump version number Eugenio Pérez
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