Re: [PATCH v8 06/46] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined

[Xiaoyao Li]

On 6/19/2026 8:31 AM, Ackerley Tng via B4 Relay wrote:
> From: Ackerley Tng <ackerleytng@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.

Well, after this series, kvm_supported_mem_attributes() is renamed to 
kvm_supported_vm_mem_attributes(), and it's still under 
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.

I don't understand it. This patch only changes the behavior of 
kvm_supported_mem_attributes(), the usage of which is guarded by 
CONFIG_KVM_VM_MEMORY_ATTRIBUTES. This is config is only visible to x86 
due to patch 03. How does it affect arm64?

> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx>
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> ---
>   virt/kvm/kvm_main.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1ccc4895a4c26..7b989b659cf82 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;
>   }