Messages in this thread | | | From | Jianyong Wu <> | Subject | RE: [PATCH] arm64/kvm: Introduce feature extension for SMCCC filter | Date | Tue, 21 Nov 2023 02:01:02 +0000 |
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> -----Original Message----- > From: Marc Zyngier <maz@kernel.org> > Sent: 2023年11月16日 22:22 > To: Cornelia Huck <cohuck@redhat.com> > Cc: Jianyong Wu <Jianyong.Wu@arm.com>; James Morse > <James.Morse@arm.com>; will@kernel.org; rmk@armlinux.org.uk; > salil.mehta@huawei.com; Suzuki Poulose <Suzuki.Poulose@arm.com>; > oliver.upton@linux.dev; linux-arm-kernel@lists.infradead.org; > kvmarm@lists.linux.dev; linux-kernel@vger.kernel.org; Justin He > <Justin.He@arm.com> > Subject: Re: [PATCH] arm64/kvm: Introduce feature extension for SMCCC filter > > 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.
Exactly. Commit e0fc6b21616dd has done for this. Ignore this patch.
Thanks Jianyong > > M. > > -- > Without deviation from the norm, progress is not possible.
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