[RFC,v1,7/9] KVM: arm64: Introduce KVM_VM_TYPE_ARM_SW_PROTECTED machine type

Commit Message

Fuad Tabba Jan. 22, 2025, 3:27 p.m. UTC

Introduce a new virtual machine type,
KVM_VM_TYPE_ARM_SW_PROTECTED, to serve as a development and
testing vehicle for Confidential (CoCo) VMs, similar to the x86
KVM_X86_SW_PROTECTED_VM type.

Initially, this is used to test guest_memfd without needing any
underlying protection.

Similar to the x86 type, this is currently only for development
and testing.  Do not use KVM_VM_TYPE_ARM_SW_PROTECTED for "real"
VMs, and especially not in production. The behavior and effective
ABI for software-protected VMs is unstable.

Signed-off-by: Fuad Tabba <[e-mail]>
---
 Documentation/virt/kvm/api.rst    |  5 +++++
 arch/arm64/include/asm/kvm_host.h | 10 ++++++++++
 arch/arm64/kvm/arm.c              |  5 +++++
 arch/arm64/kvm/mmu.c              |  3 ---
 include/uapi/linux/kvm.h          |  6 ++++++
 5 files changed, 26 insertions(+), 3 deletions(-)

Patch

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index f15b61317aad..7953b07c8c2b 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -214,6 +214,11 @@  exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects
 size of the address translated by the stage2 level (guest physical to
 host physical address translations).
 
+KVM_VM_TYPE_ARM_SW_PROTECTED is currently only for development and testing of
+confidential VMs without having underlying support. Do not use
+KVM_VM_TYPE_ARM_SW_PROTECTED for "real" VMs, and especially not in production.
+The behavior and effective ABI for software-protected VMs is unstable.
+
 
 4.3 KVM_GET_MSR_INDEX_LIST, KVM_GET_MSR_FEATURE_INDEX_LIST
 ----------------------------------------------------------
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e18e9244d17a..2fdc7e24ae8e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -380,6 +380,8 @@  struct kvm_arch {
 	 * the associated pKVM instance in the hypervisor.
 	 */
 	struct kvm_protected_vm pkvm;
+
+	unsigned long vm_type;
 };
 
 struct kvm_vcpu_fault_info {
@@ -1529,4 +1531,12 @@  void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
 #define kvm_has_s1poe(k)				\
 	(kvm_has_feat((k), ID_AA64MMFR3_EL1, S1POE, IMP))
 
+#define kvm_arch_has_private_mem(kvm)			\
+	(IS_ENABLED(CONFIG_KVM_PRIVATE_MEM) &&		\
+	 ((kvm)->arch.vm_type & KVM_VM_TYPE_ARM_SW_PROTECTED))
+
+#define kvm_arch_private_mem_inplace(kvm)		\
+	(IS_ENABLED(CONFIG_KVM_GMEM_MAPPABLE) &&	\
+	 ((kvm)->arch.vm_type & KVM_VM_TYPE_ARM_SW_PROTECTED))
+
 #endif /* __ARM64_KVM_HOST_H__ */
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index a102c3aebdbc..ecdb8db619d8 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -171,6 +171,9 @@  int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
 	int ret;
 
+	if (type & ~KVM_VM_TYPE_MASK)
+		return -EINVAL;
+
 	mutex_init(&kvm->arch.config_lock);
 
 #ifdef CONFIG_LOCKDEP
@@ -212,6 +215,8 @@  int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	bitmap_zero(kvm->arch.vcpu_features, KVM_VCPU_MAX_FEATURES);
 
+	kvm->arch.vm_type = type;
+
 	return 0;
 
 err_free_cpumask:
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index adf23618e2a0..b6cbe11dea48 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -869,9 +869,6 @@  static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
 	u64 mmfr0, mmfr1;
 	u32 phys_shift;
 
-	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 021f8ef9979b..5e10a5903a58 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -656,6 +656,12 @@  struct kvm_enable_cap {
 #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_SW_PROTECTED	(1UL << 9)
+
+#define KVM_VM_TYPE_MASK	(KVM_VM_TYPE_ARM_IPA_SIZE_MASK | \
+				 KVM_VM_TYPE_ARM_SW_PROTECTED)
+
 /*
  * ioctls for /dev/kvm fds:
  */