Re: [PATCH v8 10/46] KVM: guest_memfd: Wire up core private/shared attribute interfaces

[Ackerley Tng]

Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> writes:

> On 6/19/2026 8:31 AM, Ackerley Tng via B4 Relay wrote:
>
> [...]
>
>> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
>> index bca912db5be6e..e0e544ef47d69 100644
>> --- a/virt/kvm/guest_memfd.c
>> +++ b/virt/kvm/guest_memfd.c
>> @@ -926,6 +926,24 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
>>  EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn);
>>
>>  #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE
>> +static bool kvm_gmem_range_is_private(struct file *file, pgoff_t index,
>> +				      size_t nr_pages, struct kvm *kvm, gfn_t gfn)
>> +{
>> +	struct maple_tree *mt = &GMEM_I(file_inode(file))->attributes;
>> +	pgoff_t end = index + nr_pages - 1;
>> +	void *entry;
>> +
>> +	if (!gmem_in_place_conversion)
>> +		return kvm_range_has_vm_memory_attributes(kvm, gfn, gfn + nr_pages,
>> +							  KVM_MEMORY_ATTRIBUTE_PRIVATE,
>> +							  KVM_MEMORY_ATTRIBUTE_PRIVATE);
>> +
>> +	mt_for_each(mt, entry, index, end) {
>> +		if (xa_to_value(entry) != KVM_MEMORY_ATTRIBUTE_PRIVATE)
>> +			return false;
>> +	}
>
> Patch 1 noted that "Ensuring every index is represented in the maple tree at all times".
> So I think the queried range should not be a hole in the maple tree.
> However, there is a inconsistency: in patch 1 kvm_gmem_get_attributes() explicitly
> checks for holes, but this patch does not.
>
>> +	return true;
>> +}
>>

With Sean's suggestion for patch 1, I'll update this one to default to
the "init" state if xa_to_value(entry) is NULL.

Thanks!