Re: [RFC PATCH v2 03/21] HostMem: Add private property and associate it with RAM_KVM_GMEM

[David Hildenbrand <david@redhat.com>]

On 20.09.23 16:35, Xiaoyao Li wrote:
> On 9/20/2023 3:30 PM, Markus Armbruster wrote:
>> Xiaoyao Li <xiaoyao.li@intel.com> writes:
>>
>>> On 9/19/2023 5:46 PM, Markus Armbruster wrote:
>>>> Xiaoyao Li <xiaoyao.li@intel.com> writes:
>>>>
>>>>> From: Isaku Yamahata <isaku.yamahata@intel.com>
>>>>>
>>>>> Add a new property "private" to memory backends. When it's set to true,
>>>>> it indicates the RAMblock of the backend also requires kvm gmem.
>>>> Can you add a brief explanation why you need the property?
>>>
>>> It provides a mechanism for user to specify whether the memory can serve as private memory (need request kvm gmem).
>>
>> Yes, but why would a user want such memory?
>>
> 
> Because KVM demands it for confidential guest, e.g., TDX guest. KVM
> demands that the mem slot needs to have KVM_MEM_PRIVATE set and has
> valid gmem associated if the guest accesses it as private memory.

I think as long as there is no demand to have a TDX guest with this 
property be set to "off", then just don't add it.

With a TDX VM, it will can be implicitly active. If we ever have to 
disable it for selective memory backends, we can add the property and 
have something like on/off/auto. For now it would be "auto".

-- 
Cheers,

David / dhildenb