Re: [PATCH v9 20/41] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes

Ackerley Tng <[email protected]> Tue, 4 Aug 2026 08:39:47 -0700

Newsgroups	org.kernel.vger.linux-trace-kernel,dev.linux.lists.linux-coco,org.kernel.vger.kvm,org.kernel.vger.linux-doc,org.kernel.vger.linux-kernel,org.kernel.vger.linux-kselftest,org.kvack.linux-mm
Message-ID	<CAEvNRgErZqaLPpBveBd2VxdrS_8mjMbArL_=AhzMdikXmUU5VA@mail.gmail.com>

Xiaoyao Li <[email protected]> writes:

>
> [...snip...]
>
>> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
>> index ea2752989f8bd..df67a6188aa99 100644
>> --- a/virt/kvm/guest_memfd.c
>> +++ b/virt/kvm/guest_memfd.c
>> @@ -1137,10 +1137,12 @@ static bool kvm_range_is_private(struct file *file, pgoff_t index,
>>   {
>>   	struct inode *inode = file_inode(file);
>>
>> +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
>>   	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);
>> +#endif
>>
>>   	return kvm_gmem_range_has_attributes(inode, index, nr_pages,
>>   					     KVM_MEMORY_ATTRIBUTE_PRIVATE);
>
> With my suggestion[1] on patch 7, this diff block can be dropped.
>
> [1]
> https://lore.kernel.org/all/[email protected]/
>
> The code looks good to me,
>
> Reviewed-by: Xiaoyao Li <[email protected]>
>

I think your earlier suggestion on only defining the module_param when
CONFIG_KVM_VM_MEMORY_ATTRIBUTES is selected still applies, since it
removes an avenue for a user to turn off gmem_in_place_conversion if
the other option (VM memory attributes) isn't available.

  +#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
  +module_param(gmem_in_place_conversion, bool, 0444);
  +#endif

Given that we're now dropping the diff block as you suggested, do you
agree that we should keep this #ifdef?

>>
>> [...snip...]
>>