That's correct - it's a bug in bhyve.

Baking a proper fix will be more complicated by the fact that PCIe
cards themselves may have limitations. For example, most nVidia GPUs
have 40 bits DMA addressing capability, some 39, an a few (still
modern) ones -- just 37 [ref. nVidia "README" in the driver package].

That's a different issue - it's unlikely, if not impossible, to configure bhyve with enough RAM to hit 37 bits worth where that would become a problem. No need to worry about that.

  PCI passthru doesn't allow the BAR values to be modified (this could
be changed, but it's a lot of work for little gain).

Removing another signature of detecting virtualization and increasing
compatibility would be negligible gain? Just asking...

There are lots of BIOS/UEFI implementations out there that have the same restriction. In general, there should be no need for a guest to reprogram device BARs.

After changing the 64-bit BAR base address, did you still need the pci=nocrs option for Linux ? I'd hope this would be no longer necessary.

  # ./nvidia-smi
  No devices were found
  [  173.498953] NVRM: RmInitAdapter failed! (0x53:0x3:1856)
  [  173.499115] NVRM: rm_init_adapter failed for device bearing
minor number 0

  Looks like you're getting close :)

Hmm, I'm not seeing myself getting much closer here. Do you know
something I don't? ;) I really hope bhyve developers can spare a
bit of time on getting GPU passthrough to work... I know nothing
about these things, and where I waste half a day messing around,
the problem could be fixed in half an hour by someone who knows.

The problem is the knowledge set of graphics/GPU knowhow and equipment access, and bhyve/PCI programming, are disjoint. The time I've spent on it has been the inverse, where I feel that I've spent a half-day doing things that anyone who knew about graphics could get done in a half-hour :)

For these type of issues, joint work is best to leverage the knowledge of both sides. From my point-of-view, the work you've done has been very helpful.



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