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

[Ashish Kalra]

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;
+
+	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 {
-- 
2.17.1