Re: [PATCH for-4.17 v2] hvm/apic: repurpose the reporting of the APIC assist options

[Paul Durrant <xadimgnik@xxxxxxxxx>]

On 04/11/2022 16:18, Roger Pau Monne wrote:
> The current reporting of the hardware assisted APIC options is done by
> checking "virtualize APIC accesses" which is not very helpful, as that
> feature doesn't avoid a vmexit, instead it does provide some help in
> order to detect APIC MMIO accesses in vmexit processing.
>
> Repurpose the current reporting of xAPIC assistance to instead report
> such feature as present when there's support for "TPR shadow" and
> "APIC register virtualization" because in that case some xAPIC MMIO
> register accesses are handled directly by the hardware, without
> requiring a vmexit.
>
> For symetry also change assisted x2APIC reporting to require
> "virtualize x2APIC mode" and "APIC register virtualization", dropping
> the option to also be reported when "virtual interrupt delivery" is
> available.  Presence of the "virtual interrupt delivery" feature will
> be reported using a different option.
>
> Fixes: 2ce11ce249 ('x86/HVM: allow per-domain usage of hardware virtualized 
> APIC')
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> I find the logic in vmx_vlapic_msr_changed() hard to follow, but I
> don't want to rewrite the function logic at this point.
> ---
> Changes since v1:
>   - Fix Viridian MSR tip conditions.
Reviewed-by: Paul Durrant <paul@xxxxxxx>