[PATCH v16 16/45] KVM: arm64: CCA: Allow passing the machine type in KVM creation

Previously machine type was used purely for specifying the physical
address size of the guest. Reserve the higher bits to specify an ARM
specific machine type and declare a new type 'KVM_VM_TYPE_ARM_REALM'
used to create a realm guest.

Signed-off-by: Steven Price <[email protected]>
---
Changes since v15:
 * Specify the encoding for each VM type in the documentation.
Changes since v13:
 * Rework to use the two top bits for the machine type now that pKVM has
   merged and used the top bit for KVM_VM_TYPE_ARM_PROTECTED.
 * Update the documentation to include KVM_VM_TYPE_ARM_PROTECTED as
   well.
Changes since v9:
 * Explictly set realm.state to REALM_STATE_NONE rather than rely on the
   zeroing of the structure.
Changes since v7:
 * Add some documentation explaining the new machine type.
Changes since v6:
 * Make the check for kvm_rme_is_available more visible and report an
   error code of -EPERM (instead of -EINVAL) to make it explicit that
   the kernel supports RME, but the platform doesn't.
---
 Documentation/virt/kvm/api.rst | 21 +++++++++++++++++++--
 arch/arm64/kvm/arm.c           | 11 +++++++++++
 include/uapi/linux/kvm.h       |  7 ++++++-
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index ce588c05b26a..802601eaf560 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -181,8 +181,25 @@ flag KVM_VM_MIPS_VZ.
 ARM64:
 ^^^^^^
 
-On arm64, the physical address size for a VM (IPA Size limit) is limited
-to 40bits by default. The limit can be configured if the host supports the
+On arm64, the machine type identifier is used to encode a type and the
+physical address size for the VM. The lower byte (bits[7:0]) encodes the
+address size and the upper bits[31:30] encode a machine type. The machine
+types that might be available are:
+
+ =========================   =======   ========================================
+ Type                        [31:30]   Description
+ =========================   =======   ========================================
+ KVM_VM_TYPE_ARM_NORMAL      0b00      A standard VM
+ KVM_VM_TYPE_ARM_REALM       0b01      A "realm" VM using the Arm Confidential
+                                       Compute extensions, the VM's memory is
+                                       protected from the host.
+ KVM_VM_TYPE_ARM_PROTECTED   0b10      A "protected" VM using pKVM to
+                                       isolate the VM from the host.
+ Reserved                    0b11      Reserved for future use
+ =========================   =======   ========================================
+
+The physical address size for a VM (IPA Size limit) is limited to 40bits
+by default. The limit can be configured if the host supports the
 extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
 KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
 identifier, where IPA_Bits is the maximum width of any physical
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 6f39831dcf5d..9881fd6c511c 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -249,6 +249,17 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	mutex_unlock(&kvm->lock);
 #endif
 
+	if ((type & KVM_VM_TYPE_ARM_PROTECTED) &&
+	    (type & KVM_VM_TYPE_ARM_REALM))
+		return -EINVAL;
+
+	if (type & KVM_VM_TYPE_ARM_REALM) {
+		if (!static_branch_unlikely(&kvm_rmi_is_available))
+			return -EINVAL;
+		kvm_set_realm_state(kvm, REALM_STATE_NONE);
+		kvm->arch.is_realm = true;
+	}
+
 	kvm_init_nested(kvm);
 
 	ret = kvm_share_hyp(kvm, kvm + 1);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 0231ff174a50..adee3936d6ae 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -700,14 +700,19 @@ struct kvm_enable_cap {
  * address size for the VM. Bits[7-0] are reserved for the guest
  * PA size shift (i.e, log2(PA_Size)). For backward compatibility,
  * value 0 implies the default IPA size, 40bits.
+ *
+ * Bits[30-31] are reserved for the VM type
  */
 #define KVM_VM_TYPE_ARM_IPA_SIZE_MASK	0xffULL
 #define KVM_VM_TYPE_ARM_IPA_SIZE(x)		\
 	((x) & KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
 
+#define KVM_VM_TYPE_ARM_NORMAL		0
+#define KVM_VM_TYPE_ARM_REALM		(1UL << 30)
 #define KVM_VM_TYPE_ARM_PROTECTED	(1UL << 31)
 #define KVM_VM_TYPE_ARM_MASK		(KVM_VM_TYPE_ARM_IPA_SIZE_MASK | \
-					 KVM_VM_TYPE_ARM_PROTECTED)
+					 KVM_VM_TYPE_ARM_PROTECTED | \
+					 KVM_VM_TYPE_ARM_REALM)
 
 /*
  * ioctls for /dev/kvm fds:
-- 
2.43.0