Re: [PATCH v11 1/1] vfio/nvgpu: Add vfio pci variant module for grace hopper

Ankit Agrawal
2023-10-13T04:35:40Z

Thanks Kevin for the review.

>> > > > >
>> > > > > PCI BAR are aligned to the power-of-2, but the actual memory on the
>> > > > > device may not. A read or write access to the physical address from
>> the
>> > > > > last device PFN up to the next power-of-2 aligned physical address
>> > > > > results in reading ~0 and dropped writes.
>> > > > >
>> > > >
>> > > > my question to v10 was not answered. posted again:
>> > >
>> > > The device FW knows and tells the VM.
>> > >
>> >
>> > This driver reads the size info from ACPI and records it as
>> > nvdev->memlength.
>>
>> Yes, the ACPI tables have a copy of the size.
>
> So the ACPI copy is mainly introduced for the use of VFIO given the
> real device driver can already retrieve it from device FW?

Yes, the device mem size in ACPI DSDT is kept primarily for the vfio use.

>>
>> > But nvdev->memlength is not exposed to the userspace. How does the
>> virtual
>> > FW acquires this knowledge and then report it to the VM?
>>
>> It isn't virtual FW, I said device FW. The device itself knows how it
>> is configured and it can report details about the the memory
>> space. The VM just DMA's a RPC and asks it.
>>
>
> Interesting. Perhaps this message should be included in the commit
> message to help compose a clear picture.

I will add it, yes.

> With that,
>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>

Thanks!