[Part2 PATCH v5 08/31] KVM: Introduce KVM_MEMORY_ENCRYPT_REGISTER_REGION ioctl

[Brijesh Singh <brijesh.singh@amd.com>]

If hardware supports memory encryption then KVM_MEMORY_ENCRYPT_REGISTER_REGION
and KVM_MEMORY_ENCRYPT_UNREGISTER_REGION ioctl's can be used by userspace to
register/unregister the guest memory regions which may contain the encrypted
data (e.g guest RAM, PCI BAR, SMRAM etc).

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 Documentation/virtual/kvm/api.txt | 34 ++++++++++++++++++++++++++++++++++
 arch/x86/include/asm/kvm_host.h   |  2 ++
 arch/x86/kvm/x86.c                | 36 ++++++++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h          | 10 ++++++++++
 4 files changed, 82 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index cc1aa76ee6cd..b007998c1403 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3406,6 +3406,40 @@ Currently, this ioctl is used for issuing Secure Encrypted Virtualization (SEV)
 commands on AMD Processors. The SEV commands are defined in
 Documentation/virtual/kvm/amd-memory-encryption.txt.
 
+4.110 KVM_MEMORY_ENCRYPT_REGISTER_REGION
+
+Capability: basic
+Architectures: x86
+Type: system
+Parameters: struct kvm_enc_region (in)
+Returns: 0 on success; -1 on error
+
+This ioctl can be used to register the guest memory region which may contain
+the encrypted data (e.g guest RAM, SMRAM etc).
+
+The ioctl is used in the SEV-enabled guest. When encryption is enabled, the
+guest memory region may contain the encrypted data. The SEV memory encryption
+engine uses a tweak such that two identical plaintext pages at different
+location will have different ciphertext. So swapping or moving ciphertext of
+two pages will not result in plaintext being swapped. So relocating
+(or migrating) physical backing pages for the SEV guest will require some
+additional steps.
+
+Note: current SEV key management spec does not provide commands to swap or
+migrate (move) ciphertext pages. Hence, for now we pin the guest memory region
+registered with the ioctl.
+
+4.111 KVM_MEMORY_ENCRYPT_UNREGISTER_REGION
+
+Capability: basic
+Architectures: x86
+Type: system
+Parameters: struct kvm_enc_region (in)
+Returns: 0 on success; -1 on error
+
+This ioctl can be used to unregister the guest memory region registered with
+KVM_MEMORY_ENCRYPT_REGISTER_REGION ioctl.
+
 5. The kvm_run structure
 ------------------------
 
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 48001ca48c14..20fba8bfa727 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1063,6 +1063,8 @@ struct kvm_x86_ops {
 	void (*setup_mce)(struct kvm_vcpu *vcpu);
 
 	int (*mem_enc_op)(struct kvm *kvm, void __user *argp);
+	int (*mem_enc_register_region)(struct kvm *kvm, struct kvm_enc_region *argp);
+	int (*mem_enc_unregister_region)(struct kvm *kvm, struct kvm_enc_region *argp);
 };
 
 struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a68e8ca78dd8..95a95f24bcd7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4018,6 +4018,24 @@ static int kvm_vm_ioctl_mem_enc_op(struct kvm *kvm, void __user *argp)
 	return -ENOTTY;
 }
 
+static int kvm_vm_ioctl_mem_enc_register_region(struct kvm *kvm,
+						struct kvm_enc_region *region)
+{
+	if (kvm_x86_ops->mem_enc_register_region)
+		return kvm_x86_ops->mem_enc_register_region(kvm, region);
+
+	return -ENOTTY;
+}
+
+static int kvm_vm_ioctl_mem_enc_unregister_region(struct kvm *kvm,
+						  struct kvm_enc_region *region)
+{
+	if (kvm_x86_ops->mem_enc_unregister_region)
+		return kvm_x86_ops->mem_enc_unregister_region(kvm, region);
+
+	return -ENOTTY;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {
@@ -4282,6 +4300,24 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		r = kvm_vm_ioctl_mem_enc_op(kvm, argp);
 		break;
 	}
+	case KVM_MEMORY_ENCRYPT_REGISTER_REGION: {
+		struct kvm_enc_region region;
+
+		r = -EFAULT;
+		if (copy_from_user(&region, argp, sizeof(region)))
+			goto out;
+		r = kvm_vm_ioctl_mem_enc_register_region(kvm, &region);
+		break;
+	}
+	case KVM_MEMORY_ENCRYPT_UNREGISTER_REGION: {
+		struct kvm_enc_region region;
+
+		r = -EFAULT;
+		if (copy_from_user(&region, argp, sizeof(region)))
+			goto out;
+		r = kvm_vm_ioctl_mem_enc_unregister_region(kvm, &region);
+		break;
+	}
 	default:
 		r = -ENOTTY;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4a39d99c5f99..d595d3970390 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1359,6 +1359,16 @@ struct kvm_s390_ucas_mapping {
 /* Memory Encryption Commands */
 #define KVM_MEMORY_ENCRYPT_OP      _IOWR(KVMIO, 0xba, unsigned long)
 
+struct kvm_enc_region {
+	__u64 addr;
+	__u64 size;
+};
+
+#define KVM_MEMORY_ENCRYPT_REGISTER_REGION    _IOR(KVMIO, 0xbb,\
+						     struct kvm_enc_region)
+#define KVM_MEMORY_ENCRYPT_UNREGISTER_REGION  _IOR(KVMIO, 0xbc,\
+						     struct kvm_enc_region)
+
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
 #define KVM_DEV_ASSIGN_MASK_INTX	(1 << 2)
-- 
2.9.5