On Thu, 8 Aug 2024 at 12:23, Daniel P. Berrangé <berra...@redhat.com> wrote: > On Thu, Aug 08, 2024 at 11:15:17AM +0100, Peter Maydell wrote: > > It's not possible to use KVM with that machine type, so the > > question is a bit moot. (This also indicates that the > > interface is not very helpful -- it purports to tell the > > management layer whether it can use an accelerated in-kernel > > GIC, but because it doesn't specifiy the board type there's > > no way to provide an accurate answer. It would be useful > > to know exactly what libvirt/etc actually use this for...) > > Libvirt uses this exclusively with the arm 'virt' machine type. > > If the user didn't express any GIC preference, then if KVM is in use, > we'll pick the highest GIC version QEMU reports as supported.
You can get that without querying QEMU by asking for 'gic-version=max' if you like. > If TCG > is in use we'll always pick v2, even if QEMU reports v3 is emulatable > due to the v3 impl lacking MSI controller which we need for PCI-e Our emulated GICv3 supports the ITS which has MSI support, so I'm not sure what forcing GICv2 is getting you here. Looking at the linked RHEL bugzilla bug, I suspect this is an out-of-date policy from before we added the ITS emulation in 2021 (it's present by default in virt-2.8 and later machine types). So that is something that libvirt should update I think. thanks -- PMM
