linux-kernel - [PATCH v7 10/45] arm64: kvm: Allow passing machine type in KVM creation

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Message-ID: <20250213161426.102987-11-steven.price@arm.com>
Date: Thu, 13 Feb 2025 16:13:50 +0000
From: Steven Price <steven.price@....com>
To: kvm@...r.kernel.org,
	kvmarm@...ts.linux.dev
Cc: Steven Price <steven.price@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>,
	Will Deacon <will@...nel.org>,
	James Morse <james.morse@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Joey Gouly <joey.gouly@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Christoffer Dall <christoffer.dall@....com>,
	Fuad Tabba <tabba@...gle.com>,
	linux-coco@...ts.linux.dev,
	Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
	Gavin Shan <gshan@...hat.com>,
	Shanker Donthineni <sdonthineni@...dia.com>,
	Alper Gun <alpergun@...gle.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@...nel.org>
Subject: [PATCH v7 10/45] arm64: kvm: Allow passing 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.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Steven Price <steven.price@....com>
---
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.
---
 arch/arm64/kvm/arm.c     | 15 +++++++++++++++
 arch/arm64/kvm/mmu.c     |  3 ---
 include/uapi/linux/kvm.h | 19 +++++++++++++++----
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index df6eb5e9ca96..917ee7c674f5 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -180,6 +180,21 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	mutex_unlock(&kvm->lock);
 #endif
 
+	if (type & ~(KVM_VM_TYPE_ARM_MASK | KVM_VM_TYPE_ARM_IPA_SIZE_MASK))
+		return -EINVAL;
+
+	switch (type & KVM_VM_TYPE_ARM_MASK) {
+	case KVM_VM_TYPE_ARM_NORMAL:
+		break;
+	case KVM_VM_TYPE_ARM_REALM:
+		if (!static_branch_unlikely(&kvm_rme_is_available))
+			return -EPERM;
+		kvm->arch.is_realm = true;
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	kvm_init_nested(kvm);
 
 	ret = kvm_share_hyp(kvm, kvm + 1);
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 8cda128aafef..f8ad8f88bbb8 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -886,9 +886,6 @@ static int kvm_init_ipa_range(struct kvm *kvm,
 	if (kvm_is_realm(kvm))
 		kvm_ipa_limit = kvm_realm_ipa_limit();
 
-	if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
-		return -EINVAL;
-
 	phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
 	if (is_protected_kvm_enabled()) {
 		phys_shift = kvm_ipa_limit;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index fa8f45029dff..9cabf9b6a9b4 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -644,14 +644,25 @@ struct kvm_enable_cap {
 #define KVM_S390_SIE_PAGE_OFFSET 1
 
 /*
- * On arm64, machine type can be used to request the physical
- * 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.
+ * On arm64, machine type can be used to request both the machine type and
+ * the physical address size for the VM.
+ *
+ * Bits[11-8] are reserved for the ARM specific machine type.
+ *
+ * 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.
  */
+#define KVM_VM_TYPE_ARM_SHIFT		8
+#define KVM_VM_TYPE_ARM_MASK		(0xfULL << KVM_VM_TYPE_ARM_SHIFT)
+#define KVM_VM_TYPE_ARM(_type)		\
+	(((_type) << KVM_VM_TYPE_ARM_SHIFT) & KVM_VM_TYPE_ARM_MASK)
+#define KVM_VM_TYPE_ARM_NORMAL		KVM_VM_TYPE_ARM(0)
+#define KVM_VM_TYPE_ARM_REALM		KVM_VM_TYPE_ARM(1)
+
 #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)
+
 /*
  * ioctls for /dev/kvm fds:
  */
-- 
2.43.0