[PATCH v9 05/41] KVM: Provide generic interface for checking memory private/shared status

[Ackerley Tng via B4 Relay <devnull+ackerleytng.google.com@kernel.org>]

From: Sean Christopherson <seanjc@google.com>

Introduce a generic kvm_mem_is_private() interface using a static call to
determine if a GFN is private. This allows the implementation for checking
a GFN's private/shared status to be set at runtime.

In preparation for choosing implementations between a guest_memfd lookup
and the existing VM attribute lookup, rename the existing
VM-attribute-based check to kvm_vm_mem_is_private to emphasize that it
looks up VM attributes.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Shivank Garg <shivankg@amd.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 include/linux/kvm_host.h | 14 ++++++++++++--
 virt/kvm/kvm_main.c      | 15 +++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 297cb06302223..438567e3fa6a1 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2572,16 +2572,26 @@ bool kvm_arch_pre_set_vm_memory_attributes(struct kvm *kvm,
 bool kvm_arch_post_set_vm_memory_attributes(struct kvm *kvm,
 					    struct kvm_gfn_range *range);
 
-static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+static inline bool kvm_vm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 {
 	return kvm_get_vm_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
 }
+#endif  /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
+
+#ifdef kvm_arch_has_private_mem
+typedef bool (kvm_mem_is_private_t)(struct kvm *kvm, gfn_t gfn);
+DECLARE_STATIC_CALL(__kvm_mem_is_private, kvm_mem_is_private_t);
+
+static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
+{
+	return static_call(__kvm_mem_is_private)(kvm, gfn);
+}
 #else
 static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
 {
 	return false;
 }
-#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
+#endif /* kvm_arch_has_private_mem */
 
 #ifdef CONFIG_KVM_GUEST_MEMFD
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6f0bcab7a0ebc..80317d2c15d07 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2627,6 +2627,20 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
 }
 #endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
 
+#ifdef kvm_arch_has_private_mem
+DEFINE_STATIC_CALL_RET0(__kvm_mem_is_private, kvm_mem_is_private_t);
+EXPORT_STATIC_CALL_GPL(__kvm_mem_is_private);
+
+static void kvm_init_memory_attributes(void)
+{
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+	static_call_update(__kvm_mem_is_private, kvm_vm_mem_is_private);
+#endif
+}
+#else
+static void kvm_init_memory_attributes(void) { }
+#endif
+
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
 {
 	return __gfn_to_memslot(kvm_memslots(kvm), gfn);
@@ -6539,6 +6553,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
 	kvm_preempt_ops.sched_in = kvm_sched_in;
 	kvm_preempt_ops.sched_out = kvm_sched_out;
 
+	kvm_init_memory_attributes();
 	kvm_init_debug();
 
 	r = kvm_vfio_ops_init();

-- 
2.55.0.508.g3f0d502094-goog