On Wed, 5 Nov 2025 at 19:13, Peter Xu <[email protected]> wrote: > > On Tue, Nov 04, 2025 at 10:53:54AM +0000, Peter Maydell wrote: > > On Wed, 29 Jan 2025 at 16:03, Fabiano Rosas <[email protected]> wrote: > > > > > > From: Steve Sistare <[email protected]> > > > > > > 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=<OnOffAuto> - Enable ACPI > > append=<string> - Linux kernel command line > > aux-ram-share=<bool> > > boot=<BootConfiguration> - Boot configuration > > bus-lock-ratelimit=<uint64_t> - Set the ratelimit for the bus locks > > acquired in VMs > > confidential-guest-support=<link<confidential-guest-support>> - Set > > confidential guest scheme to support > > default-bus-bypass-iommu=<bool> > > [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=..
Yes; it was looking at the bug report about that https://gitlab.com/qemu-project/qemu/-/issues/3193 that led me to spot the aux-ram-share option. -- PMM
