On Sun, Nov 21, 2021 at 4:37 AM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > On Fri, 19 Nov 2021 04:47:53 +0000, > Reiji Watanabe <reijiw@xxxxxxxxxx> wrote: > > > > I am going to add the following comment. Does it look clear enough for you ? > > > > /* > > * This is an optional ID register specific validation function. > > * When userspace tries to set the ID register, arm64_check_features() > > * will check if the requested value indicates any features that cannot > > * be supported by KVM on the host. But, some ID register fields need > > * a special checking and this function can be used for such fields. > > * e.g. KVM_CREATE_DEVICE must be used to configure GICv3 for a guest. > > * ID_AA64PFR0_EL1.GIC shouldn't be set to 1 unless GICv3 is configured. > > There is no such requirement. GICv3 has a compatibility interface, and > although KVM doesn't make use of it, there is no reason not to expose > that GICv3 exists on the CPU even if not using it. Even more, this has > been the case forever, and making this change now would probably break > migration. Shockingly, I somehow misunderstood what read_id_reg() did for GICv3... I will use a different example for it. Thanks, Reiji
