Re: [PATCH v6 12/14] KVM: x86: Introduce KVM_PAGE_ENC_BITMAP_RESET ioctl

[Krish Sadhukhan]

On 3/29/20 11:23 PM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@xxxxxxx>
>
> This ioctl can be used by the application to reset the page
> encryption bitmap managed by the KVM driver. A typical usage
> for this ioctl is on VM reboot, on reboot, we must reinitialize
> the bitmap.
>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> ---
>   Documentation/virt/kvm/api.rst  | 13 +++++++++++++
>   arch/x86/include/asm/kvm_host.h |  1 +
>   arch/x86/kvm/svm.c              | 16 ++++++++++++++++
>   arch/x86/kvm/x86.c              |  6 ++++++
>   include/uapi/linux/kvm.h        |  1 +
>   5 files changed, 37 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 4d1004a154f6..a11326ccc51d 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -4698,6 +4698,19 @@ 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.
>   
> +4.127 KVM_PAGE_ENC_BITMAP_RESET (vm ioctl)
> +-----------------------------------------
> +
> +:Capability: basic
> +:Architectures: x86
> +:Type: vm ioctl
> +:Parameters: none
> +:Returns: 0 on success, -1 on error
> +
> +The KVM_PAGE_ENC_BITMAP_RESET is used to reset the guest's page encryption
> +bitmap during guest reboot and this is only done on the guest's boot vCPU.
> +
> +
>   5. The kvm_run structure
>   ========================
>   
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index d30f770aaaea..a96ef6338cd2 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1273,6 +1273,7 @@ struct kvm_x86_ops {
>   				struct kvm_page_enc_bitmap *bmap);
>   	int (*set_page_enc_bitmap)(struct kvm *kvm,
>   				struct kvm_page_enc_bitmap *bmap);
> +	int (*reset_page_enc_bitmap)(struct kvm *kvm);
>   };
>   
>   struct kvm_arch_async_pf {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 313343a43045..c99b0207a443 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -7797,6 +7797,21 @@ static int svm_set_page_enc_bitmap(struct kvm *kvm,
>   	return ret;
>   }
>   
> +static int svm_reset_page_enc_bitmap(struct kvm *kvm)
> +{
> +	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +
> +	if (!sev_guest(kvm))
> +		return -ENOTTY;
> +
> +	mutex_lock(&kvm->lock);
> +	/* by default all pages should be marked encrypted */
> +	if (sev->page_enc_bmap_size)
> +		bitmap_fill(sev->page_enc_bmap, sev->page_enc_bmap_size);
> +	mutex_unlock(&kvm->lock);
> +	return 0;
> +}
> +
>   static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>   {
>   	struct kvm_sev_cmd sev_cmd;
> @@ -8203,6 +8218,7 @@ 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,
> +	.reset_page_enc_bitmap = svm_reset_page_enc_bitmap,


We don't need to initialize the intel ops to NULL ? It's not initialized 
in the previous patch either.

>   };
>   
>   static int __init svm_init(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 05e953b2ec61..2127ed937f53 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5250,6 +5250,12 @@ long kvm_arch_vm_ioctl(struct file *filp,
>   			r = kvm_x86_ops->set_page_enc_bitmap(kvm, &bitmap);
>   		break;
>   	}
> +	case KVM_PAGE_ENC_BITMAP_RESET: {
> +		r = -ENOTTY;
> +		if (kvm_x86_ops->reset_page_enc_bitmap)
> +			r = kvm_x86_ops->reset_page_enc_bitmap(kvm);
> +		break;
> +	}
>   	default:
>   		r = -ENOTTY;
>   	}
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index b4b01d47e568..0884a581fc37 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1490,6 +1490,7 @@ struct kvm_enc_region {
>   
>   #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)
> +#define KVM_PAGE_ENC_BITMAP_RESET	_IO(KVMIO, 0xc7)
>   
>   /* Secure Encrypted Virtualization command */
>   enum sev_cmd_id {
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>