[PATCH v10 04/41] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined

From: Sean Christopherson <seanjc@google.com>

Explicitly guard reporting support for KVM_MEMORY_ATTRIBUTE_PRIVATE based
on kvm_arch_has_private_mem being #defined in anticipation of tracking
PRIVATE vs. SHARED state per-guest_memfd, not per-VM (to allow in-place
conversion).

guest_memfd support for memory attributes is expected to be unconditional
to avoid yet more macros (all architectures that support guest_memfd are
expected to use per-gmem attributes at some point), at which point
enumerating support KVM_MEMORY_ATTRIBUTE_PRIVATE based solely on memory
attributes being supported by KVM at-large would result in a system-scope
check (NULL @kvm) over-reporting support on arm64.

Give architectures full control over overriding the default definition of
kvm_arch_has_private_mem() by removing the coupling with
CONFIG_KVM_VM_MEMORY_ATTRIBUTES.

In a later patch, kvm_arch_has_private_mem() will be defined based on
whether architectural features are compiled in, and made orthogonal to
CONFIG_KVM_VM_MEMORY_ATTRIBUTES.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <redacted>
Reviewed-by: Binbin Wu <redacted>
Tested-by: Shivank Garg <redacted>
Signed-off-by: Ackerley Tng <redacted>
---
 include/linux/kvm_host.h | 2 +-
 virt/kvm/kvm_main.c      | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3e86cdd00e59b..e3666d0b40b74 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h

@@ -722,7 +722,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
 }
 #endif
 
-#ifndef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+#ifndef kvm_arch_has_private_mem
 static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
 {
 	return false;

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e3a77d1e6d8ae..560ff05e95959 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c

@@ -2422,8 +2422,10 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
 #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
 static u64 kvm_supported_mem_attributes(struct kvm *kvm)
 {
+#ifdef kvm_arch_has_private_mem
 	if (!kvm || kvm_arch_has_private_mem(kvm))
 		return KVM_MEMORY_ATTRIBUTE_PRIVATE;
+#endif
 
 	return 0;
 }

-- 
2.55.0.654.g21b8a5bc05-goog