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Date:      Sun, 19 Jun 2022 13:15:20 -0600
From:      John Nielsen <lists@jnielsen.net>
To:        freebsd-virtualization@freebsd.org
Cc:        c.koehne@beckhoff.com
Subject:   bhyve GPU passthrough + romfile
Message-ID:  <B3CCF8A5-AFFC-4B28-9F90-14AEAD845083@jnielsen.net>

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Hi all-

I was excited to (belatedly) see the work done in D33129 and elsewhere =
to improve GPU passthrough support with ROM emulation. However I=E2=80=99m=
 unsure how to interpret this comment: "it's only possible to use a ROM =
when using OVMF with enabled bus enumeration.=E2=80=9D Does =E2=80=9COVMF=E2=
=80=9D here refer to the normal tianocore/edk2 UEFI boot rom? How does =
one enable bus enumeration with that?

I=E2=80=99m trying to pass through an AMD GPU to a Windows 10 machine on =
bhyve. The GPU in question is the only one in the box, so if I boot both =
the host and guest via UEFI it is initialized for EFI and works fine =
when Windows attaches to and initializes it. However (and not =
surprisingly), when I reboot the VM the GPU goes in to a funky state and =
the VM doesn=E2=80=99t come up.

The behavior is the same whether or not I have a =E2=80=98rom=3D=E2=80=98 =
argument on the passthru device, so I=E2=80=99m assuming that the ROM is =
not actually being used. I=E2=80=99m further assuming that the =
aforementioned bus enumeration in the bootrom is the missing piece.

I did try rebuilding edk2-bhyve from the 202205 release. The build =
succeeded but the behavior was unchanged.

I=E2=80=99d love to get some guidance on this. Thanks!

JN

PS: Is there a known/supported way to get a GPU ROM file from FreeBSD? =
The one I have I obtained from a Linux host where this GPU was =
secondary.





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