Re: [PATCH v2] LoongArch: KVM: Advertise already-supported capabilities

[Huacai Chen]

On Mon, Aug 10, 2026 at 12:08 PM Tao Cui <cui.tao@xxxxxxxxx> wrote:
>
> Hi, Huacai
>
> I missed my Signed-off-by tag for this patch, my mistake.
> Could you append:
> Signed-off-by: Tao Cui <cuitao@xxxxxxxxxx>
> If it’s not workable, no problem at all.
Corrected.

Huacai
>
> 于 2026年8月9日 GMT+08:00 12:06:36，Huacai Chen <chenhuacai@xxxxxxxxxx> 写道：
> >Applied, thanks.
> >
> >Huacai
> >
> >On Wed, Aug 5, 2026 at 1:46 PM Tao Cui <cui.tao@xxxxxxxxx> wrote:
> >>
> >> Several LoongArch KVM features are fully implemented but were never
> >> reported through their standard KVM_CHECK_EXTENSION probes, so userspace
> >> cannot discover them.  Advertise the ones that already work and have a
> >> real consumer:
> >>
> >>   - KVM_CAP_STEAL_TIME: steal time works end-to-end (host-side record
> >>     plus guest paravirt side), and the probe returns kvm_pvtime_supported().
> >>
> >>   - KVM_CAP_VCPU_ATTRIBUTES: per-vCPU device-attribute ioctls are
> >>     implemented (CPUCFG, PVTIME control); advertise the discovery cap.
> >>
> >> This adds no new functionality; it only makes existing features
> >> discoverable via the standard probe.
> >>
> >> Signed-off-by: Tao Cui <cui.tao@xxxxxxxxx>
> >> ---
> >> Changes in v2:
> >>   - Drop KVM_CAP_IRQFD_RESAMPLE: the only consumer is VFIO INTx, which
> >>     needs IOMMU/VFIO not yet available on LoongArch.
> >>   - Drop KVM_CAP_VM_GPA_BITS: the cap implies a GPA-width setter that
> >>     LoongArch does not implement.
> >>
> >>  arch/loongarch/kvm/vm.c | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c
> >> index 1317c718f896..0a51931d6f6e 100644
> >> --- a/arch/loongarch/kvm/vm.c
> >> +++ b/arch/loongarch/kvm/vm.c
> >> @@ -122,6 +122,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >>         case KVM_CAP_IOEVENTFD:
> >>         case KVM_CAP_MP_STATE:
> >>         case KVM_CAP_SET_GUEST_DEBUG:
> >> +       case KVM_CAP_VCPU_ATTRIBUTES:
> >>                 r = 1;
> >>                 break;
> >>         case KVM_CAP_NR_VCPUS:
> >> @@ -136,6 +137,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >>         case KVM_CAP_NR_MEMSLOTS:
> >>                 r = KVM_USER_MEM_SLOTS;
> >>                 break;
> >> +       case KVM_CAP_STEAL_TIME:
> >> +               r = kvm_pvtime_supported();
> >> +               break;
> >>         default:
> >>                 r = 0;
> >>                 break;
> >>