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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id ja5-20020a170902efc500b001873aa85e1fsm1848933plb.305.2022.12.16.09.12.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Dec 2022 09:12:57 -0800 (PST) Date: Fri, 16 Dec 2022 17:12:53 +0000 From: Sean Christopherson To: Wei Wang Cc: pbonzini@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] KVM: x86: add KVM_CAP_DEVICE_CTRL Message-ID: References: <20221215115207.14784-1-wei.w.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221215115207.14784-1-wei.w.wang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 15, 2022, Wei Wang wrote: > KVM_CAP_DEVICE_CTRL allows userspace to create emulated device in KVM. > For example, userspace VFIO implementation needs to create a kvm_device > (i.e. KVM_DEV_TYPE_VFIO) on x86. So add the cap to allow userspace for > such use cases. > > Signed-off-by: Wei Wang > --- > arch/x86/kvm/x86.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 69227f77b201..1cdc4469652c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -4410,6 +4410,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > case KVM_CAP_VAPIC: > case KVM_CAP_ENABLE_CAP: > case KVM_CAP_VM_DISABLE_NX_HUGE_PAGES: > + case KVM_CAP_DEVICE_CTRL: Rather than hardcode this in x86, I think it would be better to add an #ifdef'd version in the generic check. E.g. if MIPS or RISC-V ever gains KVM_VFIO support then they'll need to enumerate KVM_CAP_DEVICE_CTRL too, and odds are we'll forget to to do. diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 13e88297f999..f70b9cea95d9 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4525,6 +4525,10 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) case KVM_CAP_BINARY_STATS_FD: case KVM_CAP_SYSTEM_EVENT_DATA: return 1; +#ifdef CONFIG_KVM_VFIO + case KVM_CAP_DEVICE_CTRL: + return 1; +#endif default: break; } The other potentially bad idea would be to detect the presence of a device_ops and delete all of the arch hooks, e.g. diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 9c5573bc4614..190e9c3b10a7 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -212,7 +212,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = vgic_present; break; case KVM_CAP_IOEVENTFD: - case KVM_CAP_DEVICE_CTRL: case KVM_CAP_USER_MEMORY: case KVM_CAP_SYNC_MMU: case KVM_CAP_DESTROY_MEMORY_REGION_WORKS: diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index 04494a4fb37a..21f9fbe96f6a 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -541,7 +541,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_ENABLE_CAP: case KVM_CAP_ONE_REG: case KVM_CAP_IOEVENTFD: - case KVM_CAP_DEVICE_CTRL: case KVM_CAP_IMMEDIATE_EXIT: case KVM_CAP_SET_GUEST_DEBUG: r = 1; diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c index 65a964d7e70d..6efe93b282e1 100644 --- a/arch/riscv/kvm/vm.c +++ b/arch/riscv/kvm/vm.c @@ -57,7 +57,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) switch (ext) { case KVM_CAP_IOEVENTFD: - case KVM_CAP_DEVICE_CTRL: case KVM_CAP_USER_MEMORY: case KVM_CAP_SYNC_MMU: case KVM_CAP_DESTROY_MEMORY_REGION_WORKS: diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index e4890e04b210..191d220b6a30 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -567,7 +567,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_ENABLE_CAP: case KVM_CAP_S390_CSS_SUPPORT: case KVM_CAP_IOEVENTFD: - case KVM_CAP_DEVICE_CTRL: case KVM_CAP_S390_IRQCHIP: case KVM_CAP_VM_ATTRIBUTES: case KVM_CAP_MP_STATE: diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 13e88297f999..99e3da9ce42d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4525,6 +4525,15 @@ static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) case KVM_CAP_BINARY_STATS_FD: case KVM_CAP_SYSTEM_EVENT_DATA: return 1; + case KVM_CAP_DEVICE_CTRL: { + int i; + + for (i = 0; i < ARRAY_SIZE(kvm_device_ops_table); ++) { + if (kvm_device_ops_table[i]) + return 1; + } + return 0; + } default: break; }