On Tue, Dec 07, 2021 at 08:51:53PM +0800, Tianyu Lan wrote:

Hi Brijesh:

Do me a favor please and learn not to top-post on a public mailing list.
Also, take the time to read Documentation/process/ before you send
upstream patches and how to work with the community in general.

We find this patch breaks AMD SEV support in the Hyper-V Isolation
VM. Hyper-V code also uses sev_es_ghcb_hv_call() to read or write msr
value. The sev_es_check_cpu_features() isn't called in the Hyper-V
code and so the ghcb_version is always 0.

If hyperv is going to expose hypervisor features, then it better report
GHCB v2. If not, then I guess < 2 or 1 or so, depending on how this is
defined.

Could you add a new parameter ghcb_version for sev_es_ghcb_hv_call()
and then caller may input ghcb_version?

No, your hypervisor needs to adhere to the spec and report proper ghcb
version. We won't be doing any accomodate-hyperv hacks.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette