linux-kernel - [RFC PATCH v1 03/37] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private

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Message-ID: <405686bacd68ce6c76aa5e6ef40f0a5324983c5b.1760731772.git.ackerleytng@google.com>
Date: Fri, 17 Oct 2025 13:11:44 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
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Subject: [RFC PATCH v1 03/37] KVM: Enumerate support for PRIVATE memory iff
 kvm_arch_has_private_mem is defined

From: Sean Christopherson <seanjc@...gle.com>

Explicitly guard reporting support for KVM_MEMORY_ATTRIBUTE_PRIVATE based
on kvm_arch_has_private_mem being #defined in anticipation of decoupling
kvm_supported_mem_attributes() from CONFIG_KVM_VM_MEMORY_ATTRIBUTES.
guest_memfd support for memory attributes will be unconditional to avoid
yet more macros (all architectures that support guest_memfd are expect to
user per-gmem attributes at some point), at which point enumerating support
KVM_MEMORY_ATTRIBUTE_PRIVATE based solely on memory attributes being
supported _somewhere_ would result in KVM over-reporting support on arm64.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 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 fddb373fcbaaf..21bf30e8d3cc1 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -721,7 +721,7 @@ 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 f73047ea4333e..591795a3fa124 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2428,8 +2428,10 @@ 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;
 }
-- 
2.51.0.858.gf9c4a03a3a-goog