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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.01.2024 15:54, Andrew Cooper wrote:
> On 09/01/2024 2:39 pm, Jan Beulich wrote:
>> Even the inner struct plan falls apart pretty quickly (or grows what
>> needs doing by too much for my taste, in the context right here):
>> While for basic_msr this works, and it would apparently also work
>> for vmfunc and tertiary exec control (the latter is itself only part
>> of a yet to be reviewed / approved patch), it doesn't for all the
>> others with split 0-setting and 1-setting halves. This is because
>> what VMX code wants are the calculated values to put in the VMCS,
>> whereas imo in the policy we'd want to store both halves (and what
>> exactly wants to be in the host policy there isn't really clear to
>> me). As a result I can't create a single uniform structure properly
>> serving both purposes. Nor could I have VMX code use the host
>> policy for most of its capability checks.
>>
>> Thought / ideas?
> 
> If it's not actually trivial, then don't worry.
> 
> The policy does need to hold the architectural representation.  The
> in-use settings need storing per-vCPU because they do (or need to me
> made to) vary based on the configuration of the VM, and because they're
> needed on every virtual vmentry when re-calculating VMCS02.

Would it help if I did a hybrid approach, i.e. move to raw/host policies
only what can be easily moved, with the rest kept as is (perhaps with
vmx_caps renamed to vmx_ctls then)?

Jan