[v6,41/43] arm64: kvm: Expose support for private memory

Commit Message

Steven Price Dec. 12, 2024, 3:56 p.m. UTC

Select KVM_GENERIC_PRIVATE_MEM and provide the necessary support
functions.

Signed-off-by: Steven Price <[e-mail]>
---
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.
---
 arch/arm64/include/asm/kvm_host.h |  6 ++++++
 arch/arm64/kvm/Kconfig            |  1 +
 arch/arm64/kvm/mmu.c              | 22 ++++++++++++++++++++++
 3 files changed, 29 insertions(+)

Patch

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 5b16e7d61de8..837e2d29609d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1408,6 +1408,12 @@  struct kvm *kvm_arch_alloc_vm(void);
 
 #define vcpu_is_protected(vcpu)		kvm_vm_is_protected((vcpu)->kvm)
 
+#ifdef CONFIG_KVM_PRIVATE_MEM
+#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.is_realm)
+#else
+#define kvm_arch_has_private_mem(kvm) false
+#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 ead632ad01b4..7bc1a2c89b3a 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -38,6 +38,7 @@  menuconfig KVM
 	select HAVE_KVM_VCPU_RUN_PID_CHANGE
 	select SCHED_INFO
 	select GUEST_PERF_EVENTS if PERF_EVENTS
+	select KVM_GENERIC_PRIVATE_MEM
 	help
 	  Support hosting virtualized guest machines.
 
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index cef7c3dcbf99..8b2d803e558a 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -2314,6 +2314,28 @@  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->only_shared = true;
+	kvm_unmap_gfn_range(kvm, range);
+
+	return false;
+}
+#endif
+
 void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
 {
 }