Re: [PATCH v4 13/24] x86/virt/seamldr: Shut down the current TDX module

[Chao Gao]

>> +static int get_tdx_sys_info_handoff(struct tdx_sys_info_handoff *sysinfo_handoff)
>> +{
>> +	int ret = 0;
>> +	u64 val;
>> +
>> +	if (!tdx_supports_runtime_update(&tdx_sysinfo))
>> +		return 0;
>
>DPAMT has a similar need to conditionally fetch metadata. The thing that is ugly
>about this is it refers to the global copy while populating the tdx_sys_info
>passed as a pointer. That is how DPAMT worked previously. I was going to change
>it to something like this for DPAMT:

Looks good. I will follow this approach.

<snip>

>Wait, looking at the later patches, in the post update caller it will refer to
>the old sysinfo instead of the new one? It assumes a new module will not lose
>runtime update ability?

Yes, no features should be removed during an update to avoid compatibility
issues. TDX module releases must guarantee this, and users should verify
compatibility before an update. If users load incompatible modules, that's
user error: the kernel doesn't prevent users from shooting themselves in
the foot.