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

Jason Gunthorpe
2023-10-10T11:34:05Z

On Tue, Oct 10, 2023 at 08:42:13AM +0000, Tian, Kevin wrote:
> > From: ankita@nvidia.com <ankita@nvidia.com>
> > Sent: Sunday, October 8, 2023 4:23 AM
> >
> > 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:
> --
> Though the variant driver emulates the access to the offset beyond
> the available memory size, how does the userspace driver or the guest
> learn to know the actual size and avoid using the invalid hole to hold
> valid data?

The device FW knows and tells the VM.

Jason