On Thu, Feb 19, 2026 at 3:43 PM Peter Maydell <[email protected]> wrote: > > On Wed, 18 Feb 2026 at 19:01, Peter Maydell <[email protected]> wrote: > > > > On Wed, 11 Feb 2026 at 12:28, Mohammadfaiz Bawa <[email protected]> wrote: > > > > > > Windows ARM64 guests detect virtio-mmio devices declared in ACPI > > > tables even when no backend is attached. This causes "Unknown > > > devices" (ACPI\LNRO0005) to appear in Device Manager. > > > > > > Until Windows fixes that by supporting, adding a new machine > > > property 'virtio-transports' to control the number of > > > virtio-mmio transports instantiated. The default remains > > > NUM_VIRTIO_TRANSPORTS (32) for backward compatibility. > > > Setting it to 0 allows users to disable virtio-mmio entirely. > > > > > > Usage: -machine virt,virtio-transports=0 > > > > > > Signed-off-by: Mohammadfaiz Bawa <[email protected]> > > > > Applied to target-arm.next, thanks -- but please could you check > > up with the ACPI spec about whether it says anything about what > > to report for empty transports? If it says we should or if it's > > just vague we should probably match the x86 microvm behaviour > > of not showing empty transports, since they can never be > > hotplugged after startup. (This might need to be tied to > > a machine-version, not sure.) Maybe we should also not report > > them in the dtb? > > Looking again at this patch, I had a couple of niggles, so > I've dropped this patch from target-arm.next for the moment. > > (1) we need to document the new property in > docs/system/arm/virt.rst. Something like
Right, sorry about missing that , I'll add the suggested documentation. > > --- a/docs/system/arm/virt.rst > +++ b/docs/system/arm/virt.rst > @@ -226,6 +226,11 @@ dtb-randomness > dtb-kaslr-seed > A deprecated synonym for dtb-randomness. > > +virtio-transports > + Set the number of virtio-mmio transports to create (between 0 and 32; > + the default is 32). Unused transports are harmless, but you can > + use this property to avoid exposing them to the guest if you wish. > + > x-oem-id > Set string (up to 6 bytes) to override the default value of field > OEMID in ACPI > table header. > > would do. > > (2) I think we should call the property virtio-mmio-transports, > to make it clearer to the user that this is MMIO-specific and > nothing to do with the much more commonly used PCI virtio. > What do you think? Yes, virtio-mmio-transports was my initial pick for the property, but I dropped it thinking it was too long.But, I think the clarity here is needed. I'll rename it. Will send v2 with both changes shortly. Thanks, Faiz > > thanks > -- PMM >
