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Wed, 05 Nov 2025 11:13:03 -0800 (PST) Received: from x1.local ([142.188.210.50]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-880828f62absm2844166d6.19.2025.11.05.11.13.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Nov 2025 11:13:02 -0800 (PST) Date: Wed, 5 Nov 2025 14:13:01 -0500 From: Peter Xu To: Peter Maydell Cc: Fabiano Rosas , qemu-devel@nongnu.org, Steve Sistare Subject: Re: [PULL 07/42] machine: aux-ram-share option Message-ID: References: <20250129160059.6987-1-farosas@suse.de> <20250129160059.6987-8-farosas@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.517, 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, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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: 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 Tue, Nov 04, 2025 at 10:53:54AM +0000, Peter Maydell wrote: > On Wed, 29 Jan 2025 at 16:03, Fabiano Rosas wrote: > > > > From: Steve Sistare > > > > Allocate auxilliary guest RAM as an anonymous file that is shareable > > with an external process. This option applies to memory allocated as > > a side effect of creating various devices. It does not apply to > > memory-backend-objects, whether explicitly specified on the command > > line, or implicitly created by the -m command line option. > > > > This option is intended to support new migration modes, in which the > > memory region can be transferred in place to a new QEMU process, by sending > > the memfd file descriptor to the process. Memory contents are preserved, > > and if the mode also transfers device descriptors, then pages that are > > locked in memory for DMA remain locked. This behavior is a pre-requisite > > for supporting vfio, vdpa, and iommufd devices with the new modes. > > Hi; I've just noticed that in this patch: > > > > @@ -1162,6 +1178,12 @@ static void machine_class_init(ObjectClass *oc, void *data) > > object_class_property_set_description(oc, "mem-merge", > > "Enable/disable memory merge support"); > > > > +#ifdef CONFIG_POSIX > > + object_class_property_add_bool(oc, "aux-ram-share", > > + machine_get_aux_ram_share, > > + machine_set_aux_ram_share); > > +#endif > > we added a new class property to the machine, but we don't > call object_class_property_set_description() to give it any > help text (compare how we handle the other properties in this > function). > > > + > > object_class_property_add_bool(oc, "usb", > > machine_get_usb, machine_set_usb); > > object_class_property_set_description(oc, "usb", > > This means that if you run "qemu-system-x86_64 -M q35,help" > you'll see that this option is missing help text: > > pc-q35-10.2-machine options: > acpi= - Enable ACPI > append= - Linux kernel command line > aux-ram-share= > boot= - Boot configuration > bus-lock-ratelimit= - Set the ratelimit for the bus locks > acquired in VMs > confidential-guest-support=> - Set > confidential guest scheme to support > default-bus-bypass-iommu= > [etc] > > Would somebody like to write a patch to add the missing > description ? Thanks for reporting, sent "[PATCH] machine: Provide a description for aux-ram-share property" just now. PS: for q35 there's another one fd-bootchk=.. -- Peter Xu