Re: [PATCH v2 2/2] KVM: TDX: Return EINVAL, not EOPNOTSUPP, for NULL INIT_MEM_REGION source

[Binbin Wu]

On 7/2/2026 1:12 AM, Sean Christopherson wrote:
> On Wed, Jul 01, 2026, Binbin Wu wrote:
>> On 7/1/2026 5:37 AM, Sean Christopherson wrote:
>>> Return EINVAL instead of EOPNOTSUPP if userspace attempts to pass a NULL
>>> pointer for the source page of INIT_MEM_REGION, so that KVM's ABI is
>>> consistent between TDX and SNP (for LAUNCH_UPDATE).  EOPNOTSUPP was chosen
>>> to be a forward-looking error code for when guest_memfd supports in-place
>>> conversion, but even when in-place conversion comes along, it's an awkward
>>> error code as KVM is deliberately choosing to disallow virtual address '0',
>>> which is technically a legal userspace address.  I.e. it's not so much a
>>> lack of support as it is that KVM reserves address '0' to simplify KVM's
>>> internal implementation.
>>
>> Nit:
>> Do you think it's worth calling this out in the documentation?
> 
> Yes, though that can be done separate since this series doesn't change ABI.
> E.g. we can probably do it opportunistically as part of the in-place conversion
> series?

Yes, make sense.