[PATCH v6 12/14] 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.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,
 };
 
 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 {
-- 
2.17.1