[PATCH v14 25/44] KVM: arm64: Expose support for private memory

[Steven Price <steven.price@arm.com>]

Select KVM_GENERIC_MEMORY_ATTRIBUTES and provide the necessary support
functions.

Signed-off-by: Steven Price <steven.price@arm.com>
---
Changes since v13:
 * Also update documentation to show that KVM_CAP_MEMORY_ATTRIBUTES is
   used on arm64.
Changes since v12:
 * Only define kvm_arch_has_private_mem() when
   CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES is set to avoid build issues
   when KVM is disabled.
Changes since v10:
 * KVM_GENERIC_PRIVATE_MEM replacd with KVM_GENERIC_MEMORY_ATTRIBUTES.
Changes since v9:
 * Drop the #ifdef CONFIG_KVM_PRIVATE_MEM guard from the definition of
   kvm_arch_has_private_mem()
Changes since v2:
 * Switch kvm_arch_has_private_mem() to a macro to avoid overhead of a
   function call.
 * Guard definitions of kvm_arch_{pre,post}_set_memory_attributes() with
   #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES.
 * Early out in kvm_arch_post_set_memory_attributes() if the WARN_ON
   should trigger.
---
 Documentation/virt/kvm/api.rst    |  2 +-
 arch/arm64/include/asm/kvm_host.h |  4 ++++
 arch/arm64/kvm/Kconfig            |  1 +
 arch/arm64/kvm/mmu.c              | 24 ++++++++++++++++++++++++
 4 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 31a5919d8d5f..a47c60490475 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6379,7 +6379,7 @@ Returns -EINVAL if called on a protected VM.
 -------------------------------
 
 :Capability: KVM_CAP_MEMORY_ATTRIBUTES
-:Architectures: x86
+:Architectures: x86, arm64
 :Type: vm ioctl
 :Parameters: struct kvm_memory_attributes (in)
 :Returns: 0 on success, <0 on error
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 39b5de03d0fe..11e7b629c950 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1531,6 +1531,10 @@ struct kvm *kvm_arch_alloc_vm(void);
 
 #define vcpu_is_protected(vcpu)		kvm_vm_is_protected((vcpu)->kvm)
 
+#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.is_realm)
+#endif
+
 int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature);
 bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
 
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 449154f9a485..4e16719fda22 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -37,6 +37,7 @@ menuconfig KVM
 	select SCHED_INFO
 	select GUEST_PERF_EVENTS if PERF_EVENTS
 	select KVM_GUEST_MEMFD
+	select KVM_GENERIC_MEMORY_ATTRIBUTES
 	help
 	  Support hosting virtualized guest machines.
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 10ca9dbe40a0..ac2a0f0106b0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -2684,6 +2684,30 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	return ret;
 }
 
+#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
+					struct kvm_gfn_range *range)
+{
+	WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm));
+	return false;
+}
+
+bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
+					 struct kvm_gfn_range *range)
+{
+	if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
+		return false;
+
+	if (range->arg.attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE)
+		range->attr_filter = KVM_FILTER_SHARED;
+	else
+		range->attr_filter = KVM_FILTER_PRIVATE;
+	kvm_unmap_gfn_range(kvm, range);
+
+	return false;
+}
+#endif
+
 void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
 {
 }
-- 
2.43.0