Re: [PATCH v8 13/46] KVM: guest_memfd: Add base support for KVM_SET_MEMORY_ATTRIBUTES2

[Ackerley Tng]

Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> writes:

> On 6/19/2026 8:31 AM, Ackerley Tng via B4 Relay wrote:
>> From: Ackerley Tng <ackerleytng@xxxxxxxxxx>
>>
>> Introduce base support for KVM_SET_MEMORY_ATTRIBUTES2 in guest_memfd, which
>> just updates attributes tracked by guest_memfd.
>>
>> Validate input fields in general. Guard usage of KVM_SET_MEMORY_ATTRIBUTES2
>> by making sure requested attributes are supported for this instance of kvm.
>>
>> A new KVM_SET_MEMORY_ATTRIBUTES2 is defined to support writes (unlike
>> KVM_SET_MEMORY_ATTRIBUTES) in addition to reads so it can provide error
>> details to userspace. This will be used in a later patch.
>>
>> The two ioctls use their corresponding structs with no overlap, but
>> backward compatibility is baked in for future support of
>> KVM_SET_MEMORY_ATTRIBUTES2 and struct kvm_memory_attributes2 in the VM
>> ioctl.
>>
>> The process of setting memory attributes is set up such that the later half
>> will not fail due to allocation. Any necessary checks are performed before
>> the point of no return.
>>
>> Co-developed-by: Vishal Annapurve <vannapurve@xxxxxxxxxx>
>> Signed-off-by: Vishal Annapurve <vannapurve@xxxxxxxxxx>
>> Co-developed-by: Sean Christoperson <seanjc@xxxxxxxxxx>
>> Signed-off-by: Sean Christoperson <seanjc@xxxxxxxxxx>
>
> s/Christoperson /Christopherson
>

Thanks!

>> Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx>
>> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
>> ---
>>  include/uapi/linux/kvm.h |  13 ++++++
>>  virt/kvm/Kconfig         |   1 +
>>  virt/kvm/guest_memfd.c   | 116 +++++++++++++++++++++++++++++++++++++++++++++++
>>  virt/kvm/kvm_main.c      |  12 +++++
>>  4 files changed, 142 insertions(+)
>>
>>
>
> [...]
>
>> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
>> index 297e4399fbd49..cfa2c78ba5fb9 100644
>> --- a/virt/kvm/Kconfig
>> +++ b/virt/kvm/Kconfig
>> @@ -102,6 +102,7 @@ config KVM_MMU_LOCKLESS_AGING
>>
>>  config KVM_GUEST_MEMFD
>>         select XARRAY_MULTI
>> +       select KVM_MEMORY_ATTRIBUTES
>
> What's this?
> This config is gone.
>

I'm surprised this compiles... I'll fix it, thanks!

>>         bool
>>