linux-kernel - Re: [PATCH v2] KVM: move KVM_CAP_DEVICE

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Message-ID: <Y9r2AGx2vR8VW4cC@google.com>
Date:   Wed, 1 Feb 2023 23:30:08 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Wei Wang <wei.w.wang@...el.com>
Cc:     pbonzini@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: move KVM_CAP_DEVICE_CTRL to the generic check

On Thu, Dec 29, 2022, Wei Wang wrote:
> KVM_CAP_DEVICE_CTRL allows userspace to check if the kvm_device
> framework (e.g. KVM_CREATE_DEVICE) is supported by KVM. Move
> KVM_CAP_DEVICE_CTRL to the generic check for the two reasons:
> 1) it already supports arch agnostic usages (i.e. KVM_DEV_TYPE_VFIO).
> For example, userspace VFIO implementation may needs to create
> KVM_DEV_TYPE_VFIO on x86, riscv, or arm etc. It is simpler to have it
> checked at the generic code than at each arch's code.
> 2) KVM_CREATE_DEVICE has been added to the generic code.

I think it's worth adding a link to the v1 patch, as that thread provides the
context for how KVM ended up unconditionally advertising the feature, e.g. instead
of trying to be more precise.

Link: https://lore.kernel.org/all/20221215115207.14784-1-wei.w.wang@intel.com

> Signed-off-by: Wei Wang <wei.w.wang@...el.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@...gle.com>