Re: [RFC PATCH v1 03/37] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined

[Binbin Wu]

On 10/18/2025 4:11 AM, Ackerley Tng wrote:

From: Sean Christopherson <sea...@google.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

 expect -> expected

user per-gmem attributes at some point), at which point enumerating support

   ^
  use

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 <sea...@google.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;

  }