On Fri, Feb 09, 2024 at 01:37:34PM -0500, Paolo Bonzini wrote:
> Allow vendor modules to provide their own attributes on /dev/kvm.
> To avoid proliferation of vendor ops, implement KVM_HAS_DEVICE_ATTR
> and KVM_GET_DEVICE_ATTR in terms of the same function. You're not
> supposed to use KVM_GET_DEVICE_ATTR to do complicated computations,
> especially on /dev/kvm.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Michael Roth <michael.roth@xxxxxxx>
> ---
> arch/x86/include/asm/kvm-x86-ops.h | 1 +
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/x86.c | 52 +++++++++++++++++++-----------
> 3 files changed, 36 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 378ed944b849..ac8b7614e79d 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -122,6 +122,7 @@ KVM_X86_OP(enter_smm)
> KVM_X86_OP(leave_smm)
> KVM_X86_OP(enable_smi_window)
> #endif
> +KVM_X86_OP_OPTIONAL(dev_get_attr)
> KVM_X86_OP_OPTIONAL(mem_enc_ioctl)
> KVM_X86_OP_OPTIONAL(mem_enc_register_region)
> KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index d271ba20a0b2..0bcd9ae16097 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1769,6 +1769,7 @@ struct kvm_x86_ops {
> void (*enable_smi_window)(struct kvm_vcpu *vcpu);
> #endif
>
> + int (*dev_get_attr)(u64 attr, u64 *val);
> int (*mem_enc_ioctl)(struct kvm *kvm, void __user *argp);
> int (*mem_enc_register_region)(struct kvm *kvm, struct kvm_enc_region *argp);
> int (*mem_enc_unregister_region)(struct kvm *kvm, struct kvm_enc_region *argp);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index bf10a9073a09..8746530930d5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4804,37 +4804,53 @@ static inline void __user *kvm_get_attr_addr(struct kvm_device_attr *attr)
> return uaddr;
> }
>
> -static int kvm_x86_dev_get_attr(struct kvm_device_attr *attr)
> +static int __kvm_x86_dev_get_attr(struct kvm_device_attr *attr, u64 *val)
> {
> - u64 __user *uaddr = kvm_get_attr_addr(attr);
> + int r;
>
> if (attr->group)
> return -ENXIO;
>
> + switch (attr->attr) {
> + case KVM_X86_XCOMP_GUEST_SUPP:
> + r = 0;
> + *val = kvm_caps.supported_xcr0;
> + break;
> + default:
> + r = -ENXIO;
> + if (kvm_x86_ops.dev_get_attr)
> + r = kvm_x86_ops.dev_get_attr(attr->attr, val);
> + break;
> + }
> +
> + return r;
> +}
> +
> +static int kvm_x86_dev_get_attr(struct kvm_device_attr *attr)
> +{
> + u64 __user *uaddr;
> + int r;
> + u64 val;
> +
> + r = __kvm_x86_dev_get_attr(attr, &val);
> + if (r < 0)
> + return r;
> +
> + uaddr = kvm_get_attr_addr(attr);
> if (IS_ERR(uaddr))
> return PTR_ERR(uaddr);
>
> - switch (attr->attr) {
> - case KVM_X86_XCOMP_GUEST_SUPP:
> - if (put_user(kvm_caps.supported_xcr0, uaddr))
> - return -EFAULT;
> - return 0;
> - default:
> - return -ENXIO;
> - }
> + if (put_user(val, uaddr))
> + return -EFAULT;
> +
> + return 0;
> }
>
> static int kvm_x86_dev_has_attr(struct kvm_device_attr *attr)
> {
> - if (attr->group)
> - return -ENXIO;
> + u64 val;
>
> - switch (attr->attr) {
> - case KVM_X86_XCOMP_GUEST_SUPP:
> - return 0;
> - default:
> - return -ENXIO;
> - }
> + return __kvm_x86_dev_get_attr(attr, &val);
> }
>
> long kvm_arch_dev_ioctl(struct file *filp,
> --
> 2.39.0
>
>
