Re: [PATCH 16/19] kvm: x86: Introduce KVM_{G|S}ET_XSAVE2 ioctl

[Paolo Bonzini <pbonzini@redhat.com>]

On 12/8/21 01:03, Yang Zhong wrote:
> From: Jing Liu <jing2.liu@intel.com>
> 
> When dynamic XSTATE features are supported, the xsave states are
> beyond 4KB. The current kvm_xsave structure and related
> KVM_{G, S}ET_XSAVE only allows 4KB which is not enough for full
> states.
> 
> Introduce a new kvm_xsave2 structure and the corresponding
> KVM_GET_XSAVE2 and KVM_SET_XSAVE2 ioctls so that userspace VMM
> can get and set the full xsave states.
> 
> Signed-off-by: Jing Liu <jing2.liu@intel.com>
> Signed-off-by: Yang Zhong <yang.zhong@intel.com>
> ---
>   arch/x86/include/uapi/asm/kvm.h |  6 ++++
>   arch/x86/kvm/x86.c              | 62 +++++++++++++++++++++++++++++++++
>   include/uapi/linux/kvm.h        |  7 +++-
>   3 files changed, 74 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 5a776a08f78c..de42a51e20c3 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -47,6 +47,7 @@
>   #define __KVM_HAVE_VCPU_EVENTS
>   #define __KVM_HAVE_DEBUGREGS
>   #define __KVM_HAVE_XSAVE
> +#define __KVM_HAVE_XSAVE2
>   #define __KVM_HAVE_XCRS
>   #define __KVM_HAVE_READONLY_MEM
>   
> @@ -378,6 +379,11 @@ struct kvm_xsave {
>   	__u32 region[1024];
>   };
>   
> +struct kvm_xsave2 {
> +	__u32 size;
> +	__u8 state[0];
> +};
> +
>   #define KVM_MAX_XCRS	16
>   
>   struct kvm_xcr {
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8b033c9241d6..d212f6d2d39a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4216,6 +4216,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>   	case KVM_CAP_DEBUGREGS:
>   	case KVM_CAP_X86_ROBUST_SINGLESTEP:
>   	case KVM_CAP_XSAVE:
> +	case KVM_CAP_XSAVE2:
>   	case KVM_CAP_ASYNC_PF:
>   	case KVM_CAP_ASYNC_PF_INT:
>   	case KVM_CAP_GET_TSC_KHZ:
> @@ -4940,6 +4941,17 @@ static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
>   				       vcpu->arch.pkru);
>   }
>   
> +static void kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
> +					  u8 *state, u32 size)
> +{
> +	if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
> +		return;
> +
> +	fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu,
> +				       state, size,
> +				       vcpu->arch.pkru);
> +}
> +
>   static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
>   					struct kvm_xsave *guest_xsave)
>   {
> @@ -4951,6 +4963,15 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
>   					      supported_xcr0, &vcpu->arch.pkru);
>   }
>   
> +static int kvm_vcpu_ioctl_x86_set_xsave2(struct kvm_vcpu *vcpu, u8 *state)
> +{
> +	if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
> +		return 0;
> +
> +	return fpu_copy_uabi_to_guest_fpstate(&vcpu->arch.guest_fpu, state,
> +					      supported_xcr0, &vcpu->arch.pkru);
> +}
> +
>   static void kvm_vcpu_ioctl_x86_get_xcrs(struct kvm_vcpu *vcpu,
>   					struct kvm_xcrs *guest_xcrs)
>   {
> @@ -5416,6 +5437,47 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>   		r = kvm_vcpu_ioctl_x86_set_xsave(vcpu, u.xsave);
>   		break;
>   	}
> +	case KVM_GET_XSAVE2: {
> +		struct kvm_xsave2 __user *xsave2_arg = argp;
> +		struct kvm_xsave2 xsave2;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&xsave2, xsave2_arg, sizeof(struct kvm_xsave2)))
> +			break;
> +
> +		u.buffer = kzalloc(xsave2.size, GFP_KERNEL_ACCOUNT);
> +
> +		r = -ENOMEM;
> +		if (!u.buffer)
> +			break;
> +
> +		kvm_vcpu_ioctl_x86_get_xsave2(vcpu, u.buffer, xsave2.size);
> +
> +		r = -EFAULT;
> +		if (copy_to_user(xsave2_arg->state, u.buffer, xsave2.size))
> +			break;
> +
> +		r = 0;
> +		break;
> +	}
> +	case KVM_SET_XSAVE2: {
> +		struct kvm_xsave2 __user *xsave2_arg = argp;
> +		struct kvm_xsave2 xsave2;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&xsave2, xsave2_arg, sizeof(struct kvm_xsave2)))
> +			break;
> +
> +		u.buffer = memdup_user(xsave2_arg->state, xsave2.size);
> +
> +		if (IS_ERR(u.buffer)) {
> +			r = PTR_ERR(u.buffer);
> +			goto out_nofree;
> +		}
> +
> +		r = kvm_vcpu_ioctl_x86_set_xsave2(vcpu, u.buffer);
> +		break;
> +	}
>   	case KVM_GET_XCRS: {
>   		u.xcrs = kzalloc(sizeof(struct kvm_xcrs), GFP_KERNEL_ACCOUNT);
>   		r = -ENOMEM;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 0c7b301c7254..603e1ca9ba09 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1132,7 +1132,9 @@ struct kvm_ppc_resize_hpt {
>   #define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
>   #define KVM_CAP_ARM_MTE 205
>   #define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
> -
> +#ifdef __KVM_HAVE_XSAVE2
> +#define KVM_CAP_XSAVE2 207
> +#endif
>   #ifdef KVM_CAP_IRQ_ROUTING
>   
>   struct kvm_irq_routing_irqchip {
> @@ -1679,6 +1681,9 @@ struct kvm_xen_hvm_attr {
>   #define KVM_GET_SREGS2             _IOR(KVMIO,  0xcc, struct kvm_sregs2)
>   #define KVM_SET_SREGS2             _IOW(KVMIO,  0xcd, struct kvm_sregs2)
>   
> +#define KVM_GET_XSAVE2		   _IOR(KVMIO,  0xcf, struct kvm_xsave2)
> +#define KVM_SET_XSAVE2		   _IOW(KVMIO,  0xd0, struct kvm_xsave2)
> +
>   struct kvm_xen_vcpu_attr {
>   	__u16 type;
>   	__u16 pad[3];
> 

Please also modify KVM_GET/SET_XSAVE to fail with ENOSPC if the 
requested size is bigger than 4096.

Paolo