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[174.91.117.74]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90ce444e2c5sm88932886d6.10.2026.08.31.10.05.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Aug 2026 10:05:22 -0700 (PDT) Date: Mon, 31 Aug 2026 13:05:14 -0400 From: Peter Xu To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: BillXiang , Alex =?utf-8?Q?Benn=C3=A9e?= , Albert Esteve , Alberto Faria , Alessandro Di Federico , Alistair Francis , Anton Johansson , Markus Armbruster , Brian Cain , "Daniel P. Berrange" , Chao Peng , cjia@nvidia.com, =?utf-8?Q?C=C3=A9dric?= Le Goater , cw@f00f.org, dbarboza@qti.qualcomm.com, Demi Marie Obenour , dhedde@kalrayinc.com, Eric Blake , eblot@rivosinc.com, "Edgar E. Iglesias" , Eduardo Habkost , Elena Ufimtseva , Auger Eric , felipe@nutanix.com, helge.deller@googlemail.com, Alyssa Ross , iggy@theiggy.com, Warner Losh , jacob.oursland@gmail.com, Jan Kiszka , Jason Gunthorpe , jidong.xiao@gmail.com, Jim Shu , Joao Martins , Konrad Rzeszutek Wilk , Luc Michel , Manos Pitsidianakis , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , matthieu@minio.io, Max Chou , Mark Burton , "Ho, Nelson" , Paul Walmsley , Paolo Bonzini , Peter Maydell , QEMU Developers , Roberto Campesato , Richard Henderson , Shameerali Kolothum Thodi , Bernhard Beschow , Stefan Hajnoczi , Thomas Huth , utsingh@redhat.com, Wei Wang , z.huo@139.com, LIU Zhiwei , zwu.kernel@gmail.com Subject: Re: KVM/QEMU community call tomorrow - agenda items? Message-ID: References: <877bl6eoqv.fsf@draig.linaro.org> <413b9ba2-20cf-4af6-9998-be46da277c84@lanxincomputing.com> <48cef34d-18c1-4b8c-a75d-19d1d1321634@oss.qualcomm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <48cef34d-18c1-4b8c-a75d-19d1d1321634@oss.qualcomm.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Aug 31, 2026 at 05:46:12PM +0200, Philippe Mathieu-Daudé wrote: > On 31/8/26 13:49, BillXiang wrote: > > > How about discussing the patch[1]: > > "virtio: Add aligned ld/st accessors for vring". > > > > As pointed out in the patch, this has been a long-standing issue. It is > > now necessary to introduce atomic accessors for fields that require > > atomicity, such as the avail_idx field in virtio. This support is > > especially crucial for architectures like RISC-V, which do not natively > > support misaligned memory accesses. > > > > I'm particularly eager to receive more suggestions for it. I saw the last email was from me.. https://lore.kernel.org/qemu-devel/aoxiBB2Wn8NiL5s6@x1.local/ I believe that was what PeterM suggested. I think Richard also at least partly agrees. so I thought we had at least partial consensus on the rough idea, if not exactly how. I confess I haven't fully got the latter part of Richard's comment, regarding the possibility to reuse accel/tcg/ldst_atomicity.c.inc: that path seems to invole a guest CPU context, where in the case of reading virtio ring it is from host and it has no guest CPU context. But I think we can continue the discussion on the list in that thread. > > This is a very technical topic, not sure if the community call will > be a better place than the mailing list, in particular if no virtio / > atomic expert developers appears. We'll see :) Yes, I had such similar feeling that the problem was not yet blocked by something that a video call would better help.. For example, I still want to double check if that change would work for your current use case, it will at least verify the thought, no matter if we want to use it or not. Thanks, -- Peter Xu