Re: [PATCH v6 11/14] KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl

[Krish Sadhukhan]

On 3/29/20 11:22 PM, Ashish Kalra wrote:
> From: Brijesh Singh <Brijesh.Singh@xxxxxxx>
>
> The ioctl can be used to set page encryption bitmap for an
> incoming guest.
>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: "Radim KrÄmÃÅ" <rkrcmar@xxxxxxxxxx>
> Cc: Joerg Roedel <joro@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> ---
>   Documentation/virt/kvm/api.rst  | 22 +++++++++++++++++
>   arch/x86/include/asm/kvm_host.h |  2 ++
>   arch/x86/kvm/svm.c              | 42 +++++++++++++++++++++++++++++++++
>   arch/x86/kvm/x86.c              | 12 ++++++++++
>   include/uapi/linux/kvm.h        |  1 +
>   5 files changed, 79 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 8ad800ebb54f..4d1004a154f6 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4675,6 +4675,28 @@ or shared. The bitmap can be used during the guest migration, if the page
>   is private then userspace need to use SEV migration commands to transmit
>   the page.
>   
> +4.126 KVM_SET_PAGE_ENC_BITMAP (vm ioctl)
> +---------------------------------------
> +
> +:Capability: basic
> +:Architectures: x86
> +:Type: vm ioctl
> +:Parameters: struct kvm_page_enc_bitmap (in/out)
> +:Returns: 0 on success, -1 on error
> +
> +/* for KVM_SET_PAGE_ENC_BITMAP */
> +struct kvm_page_enc_bitmap {
> +	__u64 start_gfn;
> +	__u64 num_pages;
> +	union {
> +		void __user *enc_bitmap; /* one bit per page */
> +		__u64 padding2;
> +	};
> +};
> +
> +During the guest live migration the outgoing guest exports its page encryption
> +bitmap, the KVM_SET_PAGE_ENC_BITMAP can be used to build the page encryption
> +bitmap for an incoming guest.
>   
>   5. The kvm_run structure
>   ========================
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 27e43e3ec9d8..d30f770aaaea 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1271,6 +1271,8 @@ struct kvm_x86_ops {
>   				  unsigned long sz, unsigned long mode);
>   	int (*get_page_enc_bitmap)(struct kvm *kvm,
>   				struct kvm_page_enc_bitmap *bmap);
> +	int (*set_page_enc_bitmap)(struct kvm *kvm,
> +				struct kvm_page_enc_bitmap *bmap);
>   };
>   
>   struct kvm_arch_async_pf {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index bae783cd396a..313343a43045 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -7756,6 +7756,47 @@ static int svm_get_page_enc_bitmap(struct kvm *kvm,
>   	return ret;
>   }
>   
> +static int svm_set_page_enc_bitmap(struct kvm *kvm,
> +				   struct kvm_page_enc_bitmap *bmap)
> +{
> +	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +	unsigned long gfn_start, gfn_end;
> +	unsigned long *bitmap;
> +	unsigned long sz, i;
> +	int ret;
> +
> +	if (!sev_guest(kvm))
> +		return -ENOTTY;
> +
> +	gfn_start = bmap->start_gfn;
> +	gfn_end = gfn_start + bmap->num_pages;


Same comment as the previous one. Do we continue if num_pages is zero ?

> +
> +	sz = ALIGN(bmap->num_pages, BITS_PER_LONG) / 8;
> +	bitmap = kmalloc(sz, GFP_KERNEL);
> +	if (!bitmap)
> +		return -ENOMEM;
> +
> +	ret = -EFAULT;
> +	if (copy_from_user(bitmap, bmap->enc_bitmap, sz))
> +		goto out;
> +
> +	mutex_lock(&kvm->lock);
> +	ret = sev_resize_page_enc_bitmap(kvm, gfn_end);
> +	if (ret)
> +		goto unlock;
> +
> +	i = gfn_start;
> +	for_each_clear_bit_from(i, bitmap, (gfn_end - gfn_start))
> +		clear_bit(i + gfn_start, sev->page_enc_bmap);
> +
> +	ret = 0;
> +unlock:
> +	mutex_unlock(&kvm->lock);
> +out:
> +	kfree(bitmap);
> +	return ret;
> +}
> +
>   static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>   {
>   	struct kvm_sev_cmd sev_cmd;
> @@ -8161,6 +8202,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
>   
>   	.page_enc_status_hc = svm_page_enc_status_hc,
>   	.get_page_enc_bitmap = svm_get_page_enc_bitmap,
> +	.set_page_enc_bitmap = svm_set_page_enc_bitmap,
>   };
>   
>   static int __init svm_init(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3c3fea4e20b5..05e953b2ec61 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5238,6 +5238,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
>   			r = kvm_x86_ops->get_page_enc_bitmap(kvm, &bitmap);
>   		break;
>   	}
> +	case KVM_SET_PAGE_ENC_BITMAP: {
> +		struct kvm_page_enc_bitmap bitmap;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&bitmap, argp, sizeof(bitmap)))
> +			goto out;
> +
> +		r = -ENOTTY;
> +		if (kvm_x86_ops->set_page_enc_bitmap)
> +			r = kvm_x86_ops->set_page_enc_bitmap(kvm, &bitmap);
> +		break;
> +	}
>   	default:
>   		r = -ENOTTY;
>   	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index db1ebf85e177..b4b01d47e568 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1489,6 +1489,7 @@ struct kvm_enc_region {
>   #define KVM_S390_CLEAR_RESET	_IO(KVMIO,   0xc4)
>   
>   #define KVM_GET_PAGE_ENC_BITMAP	_IOW(KVMIO, 0xc5, struct kvm_page_enc_bitmap)
> +#define KVM_SET_PAGE_ENC_BITMAP	_IOW(KVMIO, 0xc6, struct kvm_page_enc_bitmap)
>   
>   /* Secure Encrypted Virtualization command */
>   enum sev_cmd_id {
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>