Messages in this thread | | | Date | Thu, 16 Nov 2023 14:21:37 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH] arm64/kvm: Introduce feature extension for SMCCC filter |
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On Thu, 16 Nov 2023 13:08:58 +0000, Cornelia Huck <cohuck@redhat.com> wrote: > > On Thu, Nov 16 2023, Jianyong Wu <jianyong.wu@arm.com> wrote: > > > 821d935c87b introduces support for userspace SMCCC filtering, but lack > > of a way to tell userspace if we have this feature. Add a corresponding > > feature extension can resolve this issue. > > > > For example, the incoming feature Vcpu Hotplug needs the SMCCC filter. > > As there is no way to check this feature, VMM will run into error when > > it calls this feature on an old kernel. It's bad for backward compatible. > > Can't you simply query via KVM_HAS_DEVICE_ATTR whether the SMCCC > filtering controls exist?
Quite. Commit e0fc6b21616dd introduced it for that exact purpose, specifically to prevent adding more of these capabilities when there is a corresponding attribute that can be readily queried.
M.
-- Without deviation from the norm, progress is not possible.
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