Re: [PATCH v6 03/43] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined

[Fuad Tabba]

On Thu, 7 May 2026 at 21:22, Ackerley Tng via B4 Relay
<devnull+ackerleytng.google.com@xxxxxxxxxx> wrote:
>
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
>
> 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 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 _somewhere_ would result in KVM over-reporting support on arm64.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>

Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx>

Cheers,
/fuad

> ---
>  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 7b9faa3545300..7d079f9701346 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 306153abbafa5..abb9cfa3eb04d 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2421,8 +2421,10 @@ 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;
>  }
>
> --
> 2.54.0.563.g4f69b47b94-goog
>
>