>-----Original Message-----
>From: Nicolin Chen <nicol...@nvidia.com>
>Subject: Re: [PATCH v5 02/21] hw/pci: Introduce
>pci_device_get_viommu_cap()
>
>On Fri, Aug 29, 2025 at 01:54:50AM +0000, Duan, Zhenzhong wrote:
>> >>On 2025/8/27 23:30, Nicolin Chen wrote:
>> >>> On Wed, Aug 27, 2025 at 02:32:42PM +0200, Eric Auger wrote:
>> >>>> On 8/27/25 2:30 PM, Yi Liu wrote:
>> >>>>> On 2025/8/27 19:22, Eric Auger wrote:
>> >>>>>>> TBH. I'm hesitating to name it as get_viommu_cap. The scope is a
>> >little
>> >>>>>>> larger than what we want so far. So I'm wondering if it can be
>done
>> >>>>>>> in a
>> >>>>>>> more straightforward way. e.g. just a bool op named
>> >>>>>>> iommu_nested_wanted(). Just an example, maybe better naming.
>We
>> >>can
>> >>>>>>> extend the op to be returning a u64 value in the future when we
>see
>> >>>>>>> another request on VFIO from vIOMMU.
>> >>>>>> personnally I am fine with the bitmask which looks more future
>proof.
>> >>>>>
>> >>>>> not quite sure if there is another info that needs to be checked in
>> >>>>> this "VFIO asks vIOMMU" manner. Have you seen one beside this
>> >>>>> nested hwpt requirement by vIOMMU?
>> >>>>
>> >>>> I don't remember any at this point. But I guess with ARM CCA device
>> >>>> passthrough we might have other needs
>> >>>
>> >>> Yea. A Realm vSMMU instance won't allocate IOAS/HWPT. So it will
>> >>> ask the core to bypass those allocations, via the same op.
>> >>>
>> >>> I don't know: does "get_viommu_flags" sound more fitting to have
>> >>> a clear meaning of "want"?
>> >>>
>> >>> VIOMMU_FLAG_WANT_NESTING_PARENT
>> >>> VIOMMU_FLAG_WANT_NO_IOAS
>> >>>
>> >>> At least, the 2nd one being a "cap" wouldn't sound nice to me..
>> >>
>> >>this looks good to me.
>> >
>> >OK, will do s/get_viommu_cap/get_viommu_flags and
>> >s/VIOMMU_CAP_HW_NESTED/
>VIOMMU_FLAG_WANT_NESTING_PARENT if
>> >no more suggestions.
>>
>> I just noticed this change will conflict with your suggestion of using
>HW_NESTED terminology.
>> Let me know if you agree with this change or not?
>
>It wouldn't necessarily conflict. VIOMMU_FLAG_WANT_NESTING_PARENT
>is a request, interchangeable with VIOMMU_FLAG_SUPPORT_HW_NESTED,
>i.e. a cap.
>
>At the end of the day, they are fundamentally the same thing that
>is to tell the core to allocate a nesting parent HWPT. The former
>one is just more straightforward, avoiding confusing terms such as
>"stage-1" and "nested".
>
>IMHO, you wouldn't even need the comments in the other thread, as
>the flag explains clearly what it wants and what the core is doing.
>
>Also, once you use the "want" one, the "HW_NESTED" terminology will
>not exist in the code.
OK, will use the *_flags and _WANT_* style, do you have suggestions for the
name of vfio_device_viommu_get_nested() since "HW_NESTED" terminology will not
exist, what about vfio_device_get_viommu_flags_W_N_P()?
Thanks
Zhenzhong
