Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH v11 1/1] vfio/nvgpu: Add vfio pci variant module for grace hopper | Date | Fri, 13 Oct 2023 03:43:54 +0000 |
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> From: Jason Gunthorpe <jgg@nvidia.com> > Sent: Wednesday, October 11, 2023 8:00 PM > > On Wed, Oct 11, 2023 at 02:00:30AM +0000, Tian, Kevin wrote: > > > From: Jason Gunthorpe <jgg@nvidia.com> > > > Sent: Tuesday, October 10, 2023 7:34 PM > > > > > > 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: > > > > > > 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?
> > > 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.
With that,
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
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