Re: [XEN PATCH v2 14/15] iommu/vt-d: guard vmx_pi_hooks_* calls with cpu_has_vmx

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.05.2024 02:54, Stefano Stabellini wrote:
> On Wed, 15 May 2024, Sergiy Kibrik wrote:
>> VMX posted interrupts support can now be excluded from x86 build along with
>> VMX code itself, but still we may want to keep the possibility to use
>> VT-d IOMMU driver in non-HVM setups.
>> So we guard vmx_pi_hooks_{assign/deassign} with some checks for such a case.
>>
>> No functional change intended here.
>>
>> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
> 
> I know that Andrew was keep on having a separate Kconfig option for
> VT-D, separate from VMX. But still, couldn't we make the VT-D Kconfig
> option depending on CONFIG_VMX?
> 
> To me, VT-D should require VMX, without VMX it should not be possible to
> enable VT-D.
> 
> This comment goes in the same direction of my previous comment regarding
> the vpmu: we are trying to make things more configurable and flexible
> and that's good, but we don't necessary need to make all possible
> combination work. VT-D without VMX is another one of those combination
> that I would only enable after a customer asks.

Well. Imo again the configuration should be permitted. VMX and INTEL_IOMMU
ought to be default to INTEL, but permit being turned on/off in all cases.
(That's btw part of the reason why I continue to be unhappy with it being
INTEL where really INTEL_CPU was meant. If what is INTEL now would be
INTEL_CPU, INTEL could be an umbrella option for all three, or two if we
were to tie VMX to INTEL_CPU.)

Jan