Re: [PATCH v2 08/15] VMX: convert vmx_basic_msr

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 24/11/2023 8:41 am, Jan Beulich wrote:
> ... to a struct field, which is then going to be accompanied by other
> capability/control data presently living in individual variables. As
> this structure isn't supposed to be altered post-boot, put it in
> .data.ro_after_init right away.
>
> Suggested-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

For (usable) nested virt, we're going to need the VMX MSRs, in their
architectural form, in struct cpu_policy.  And just like CPUID features,
I want it to end up with nice bitfields to use.

Looking through the rest of this series, vmx_caps ends up almost in
architectural form.

Could I talk you into having a "struct vmx_msrs" (or similar - 'caps'
doesn't feel quite right here) in the policy object, and also
instantiating one instance of it for this purpose here?

AFAICT, it would only be a minor deviation to the latter half of this
series, but it would be an excellent start to fixing nested virt - and
getting this data in the policy really is the first task in getting the
ball rolling on nested virt.

I don't mind about serialising/de-serialsing it - that still has a bit
of userspace complexity to work out, and depends on some of the cleanup
still needing a repost.

If you don't want to take the added space in cpu_policy yet, how about
having the declaration there and just forgo instantiating the subobject
in the short term?

~Andrew