[PATCH v7 42/45] arm64: kvm: Expose support for private memory

Steven Price
2025-02-13T16:17:58Z

Select KVM_GENERIC_PRIVATE_MEM and provide the necessary support
functions.

Signed-off-by: Steven Price <steven.price@arm.com>
---
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(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 6f05aecfda99..df9497998ed5 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1433,6 +1433,12 @@ 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 a849ff66e584..2f3006421b76 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -2352,6 +2352,28 @@ 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)
{
}
--
2.43.0