RE: [PATCH v8 1/1] vfio/nvgpu: Add vfio pci variant module for grace hopper

[Tian, Kevin]

> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Friday, September 8, 2023 8:16 PM
> 
> On Fri, Sep 08, 2023 at 01:50:36AM -0700, Christoph Hellwig wrote:
> > On Thu, Sep 07, 2023 at 10:04:10PM -0600, Alex Williamson wrote:
> > > > I think it really depends on what the qemu side wants to do..
> > >
> > > Ok, I thought you had been one of the proponents of the fake BAR
> > > approach as more resembling CXL.
> 
> Yes, I do prefer this because it is ultimately simpler on the qemu and
> VM side. This ACPI tinkering is not nice.
> 
> > > Do we need to reevaluate that the tinkering with the VM machine
> > > topology and firmware tables would better align to a device
> > > specific region that QEMU inserts into the VM address space so
> > > that bare metal and virtual machine versions of this device look
> > > more similar?  Thanks,
> 
> > Yes, providing something to a VM that doesn't look anything like the
> > underlying hardware feels pretty strange.
> 
> I don't see the goal as perfect emulation of the real HW.
> 
> Aiming for minimally disruptive to the ecosystem to support this
> quirky pre-CXL HW.
> 
> Perfect emulation would need a unique VFIO uAPI and more complex qemu
> changes, and it really brings nothing of value.
> 

Does it mean that this requires maintaining a new guest driver
different from the existing one on bare metal?