[PATCH 12/12] KVM: x86: Introduce KVM_PAGE_ENC_BITMAP_RESET ioctl

[Ashish Kalra]

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.txt  | 11 +++++++++++
 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, 35 insertions(+)

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index d4e29a457e80..bf0fd3c2ea07 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -4261,6 +4261,17 @@ 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.
 
+4.122 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 698ea92290af..746c9c84d14a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1262,6 +1262,7 @@ 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 a710a6a2d18c..1659539b1873 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7756,6 +7756,21 @@ 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;
@@ -8151,6 +8166,7 @@ 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,
 };
 
 static int __init svm_init(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a1ac5b8c5cd7..eeb2a3dfeb02 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5237,6 +5237,12 @@ 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 2f36afd11e0e..4001c22cb36b 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, 0xc2, struct kvm_page_enc_bitmap)
 #define KVM_SET_PAGE_ENC_BITMAP	_IOW(KVMIO, 0xc3, struct kvm_page_enc_bitmap)
+#define KVM_PAGE_ENC_BITMAP_RESET	_IO(KVMIO, 0xc4)
 
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {
-- 
2.17.1