[PATCH v10 10/16] KVM: x86: Introduce KVM_GET_SHARED_PAGES_LIST ioctl

[Ashish Kalra]

From: Brijesh Singh <brijesh.singh@xxxxxxx>

The ioctl is used to retrieve a guest's shared pages list.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: "Radim Krčmář" <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>
Co-developed-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 Documentation/virt/kvm/api.rst  | 24 ++++++++++++++++
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/svm/sev.c          | 49 +++++++++++++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c          |  1 +
 arch/x86/kvm/svm/svm.h          |  1 +
 arch/x86/kvm/x86.c              | 12 ++++++++
 include/uapi/linux/kvm.h        |  9 ++++++
 7 files changed, 98 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 99ceb978c8b0..59ef537c0cdd 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4677,6 +4677,30 @@ This ioctl resets VCPU registers and control structures according to
 the clear cpu reset definition in the POP. However, the cpu is not put
 into ESA mode. This reset is a superset of the initial reset.
 
+4.125 KVM_GET_SHARED_PAGES_LIST (vm ioctl)
+---------------------------------------
+
+:Capability: basic
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_shared_pages_list (in/out)
+:Returns: 0 on success, -1 on error
+
+/* for KVM_GET_SHARED_PAGES_LIST */
+struct kvm_shared_pages_list {
+	int __user *pnents;
+	void __user *buffer;
+	__u32 size;
+};
+
+The encrypted VMs have the concept of private and shared pages. The private
+pages are encrypted with the guest-specific key, while the shared pages may
+be encrypted with the hypervisor key. The KVM_GET_SHARED_PAGES_LIST can
+be used to get guest's shared/unencrypted memory regions list.
+This list can be used during the guest migration. If the page
+is private then the userspace need to use SEV migration commands to transmit
+the page.
+
 
 4.125 KVM_S390_PV_COMMAND
 -------------------------
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2da5f5e2a10e..cd354d830e13 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1303,6 +1303,8 @@ struct kvm_x86_ops {
 	void (*vcpu_deliver_sipi_vector)(struct kvm_vcpu *vcpu, u8 vector);
 	int (*page_enc_status_hc)(struct kvm *kvm, unsigned long gpa,
 				  unsigned long sz, unsigned long mode);
+	int (*get_shared_pages_list)(struct kvm *kvm,
+				     struct kvm_shared_pages_list *list);
 };
 
 struct kvm_x86_nested_ops {
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 55c628df5155..701d74c8b15b 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -50,6 +50,11 @@ struct shared_region {
 	unsigned long gfn_start, gfn_end;
 };
 
+struct shared_region_array_entry {
+	unsigned long gfn_start;
+	unsigned long gfn_end;
+};
+
 static int sev_flush_asids(void)
 {
 	int ret, error = 0;
@@ -1622,6 +1627,50 @@ int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
 	return ret;
 }
 
+int svm_get_shared_pages_list(struct kvm *kvm,
+			      struct kvm_shared_pages_list *list)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct shared_region_array_entry *array;
+	struct shared_region *pos;
+	int ret, nents = 0;
+	unsigned long sz;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	if (!list->size)
+		return -EINVAL;
+
+	if (!sev->shared_pages_list_count)
+		return put_user(0, list->pnents);
+
+	sz = sev->shared_pages_list_count * sizeof(struct shared_region_array_entry);
+	if (sz > list->size)
+		return -E2BIG;
+
+	array = kmalloc(sz, GFP_KERNEL);
+	if (!array)
+		return -ENOMEM;
+
+	mutex_lock(&kvm->lock);
+	list_for_each_entry(pos, &sev->shared_pages_list, list) {
+		array[nents].gfn_start = pos->gfn_start;
+		array[nents++].gfn_end = pos->gfn_end;
+	}
+	mutex_unlock(&kvm->lock);
+
+	ret = -EFAULT;
+	if (copy_to_user(list->buffer, array, sz))
+		goto out;
+	if (put_user(nents, list->pnents))
+		goto out;
+	ret = 0;
+out:
+	kfree(array);
+	return ret;
+}
+
 int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index bb249ec625fc..533ce47ff158 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4538,6 +4538,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.vcpu_deliver_sipi_vector = svm_vcpu_deliver_sipi_vector,
 
 	.page_enc_status_hc = svm_page_enc_status_hc,
+	.get_shared_pages_list = svm_get_shared_pages_list,
 };
 
 static struct kvm_x86_init_ops svm_init_ops __initdata = {
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 6437c1fa1f24..6a777c61373c 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -477,6 +477,7 @@ int nested_svm_exit_special(struct vcpu_svm *svm);
 void sync_nested_vmcb_control(struct vcpu_svm *svm);
 int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
 			   unsigned long npages, unsigned long enc);
+int svm_get_shared_pages_list(struct kvm *kvm, struct kvm_shared_pages_list *list);
 
 extern struct kvm_x86_nested_ops svm_nested_ops;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2f17f0f9ace7..acfec2ae1402 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5719,6 +5719,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	case KVM_X86_SET_MSR_FILTER:
 		r = kvm_vm_ioctl_set_msr_filter(kvm, argp);
 		break;
+	case KVM_GET_SHARED_PAGES_LIST: {
+		struct kvm_shared_pages_list list;
+
+		r = -EFAULT;
+		if (copy_from_user(&list, argp, sizeof(list)))
+			goto out;
+
+		r = -ENOTTY;
+		if (kvm_x86_ops.get_shared_pages_list)
+			r = kvm_x86_ops.get_shared_pages_list(kvm, &list);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index c4e195a4220f..0529ba80498a 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -544,6 +544,13 @@ struct kvm_clear_dirty_log {
 	};
 };
 
+/* for KVM_GET_SHARED_PAGES_LIST */
+struct kvm_shared_pages_list {
+	int __user *pnents;
+	void __user *buffer;
+	__u32 size;
+};
+
 /* for KVM_SET_SIGNAL_MASK */
 struct kvm_signal_mask {
 	__u32 len;
@@ -1565,6 +1572,8 @@ struct kvm_pv_cmd {
 /* Available with KVM_CAP_DIRTY_LOG_RING */
 #define KVM_RESET_DIRTY_RINGS		_IO(KVMIO, 0xc7)
 
+#define KVM_GET_SHARED_PAGES_LIST	_IOW(KVMIO, 0xc8, struct kvm_shared_pages_list)
+
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {
 	/* Guest initialization commands */
-- 
2.17.1