bhyve Can an Intel GPU passed/thru thru BHYVE act as a FRAMEBUFFER (without attaching it to a monitor thru an HDMI port) ? if yes,how ?

[ZioMario]

Hello.

for the first time I’ve been able to passthru my Intel GPU to an Ubuntu 22.10 vm and my monitor turned on. It didn’t work yet because my monitor is very old. It didn’t turn on neither physically because I think it needs to warm up a little bit,like every old monitor ; maybe there were also different problems that prevented it from turning on. So,now that I’m sure that there aren’t bugs either in the FreeBSD side nor in the Linux side,we can jump to the main question. How to configure XORG so that the Intel GPU can act as a framebuffer and the nvidia RTX 2080 ti GPU as PRIME RENDER OFFLOAD ? I ask this because I have already ascertained that the FBDEV framebuffer can't be used together with the nvidia GPU and the configuration below does not work :

Section "ServerLayout"
Identifier "layout"
Screen 0 "iGPU"
EndSection

Section "Device"
Identifier "iGPU"
Driver "modesetting"
BusID "PCI:0:6:0
EndSection

Section "Screen"
  Identifier "iGPU"
  Device "iGPU"
EndSection

Section "ServerLayout"
  Identifier "layout"
  Option "AllowNVIDIAGPUScreens"
EndSection

For this reason I can’t have the FBDEV / VNC framebuffer as first and the nvidia GPU as secondary (using one only monitor). On the nvidia forum a developer told me that if I use the intel GPU as a framebuffer instead of the FBDEV and the nvidia as secondary,it would work. So,how can I achieve this goal ? I want to do this because I can’t use two monitors. My secondary monitor is old and I have placed it in another room. I have one only monitor and inside it I want to see the Ubuntu VM inside a window and I want to use the nvidia GPU only for rendering videos and pictures with stable diffusion. If I make the passthru the intel GPU without attaching a monitor to its HDMI port,it will work or not ? I suspect that I'm forced to use a monitor. Anyway I've got an idea. I've thought to use a dummy HDMI plug. I've attached two dummy HDMI plugs to my PC,one on the Intel HDMI port and the other one on the HDMI port of the RTX 2080 ti (while my host os is using the 3 GPUs [nvidia gtx 1060 configured as primary and default GPU on the BIOS). I performed a fresh installation of Ubuntu as a VM passing thru all my GPUs. Below you can see the parameters used :

bhyve -S -c sockets=1,cores=2,threads=2 -m 4G -w -H -A \
-s 0,hostbridge \
-s 1,ahci-cd,/mnt/$vmdisk1'p2'/bhyve/iso/Linux/Ubuntu-22.10-desktop-amd64.iso,bootindex=1 \
-s 2,virtio-blk,/mnt/$vmdisk1'p2'/bhyve/img/Linux/Ubuntu-2210-new.img \
-s 6,fbuf,tcp=0.0.0.0:5920,w=1600,h=950,wait \
-s 7,passthru,0/2/0 \
-s 8:0,passthru,2/0/0 \
-s 8:1,passthru,2/0/1 \
-s 8:2,passthru,2/0/2 \
-s 8:3,passthru,2/0/3 \
-s 10,virtio-net,tap20 \
-s 11,virtio-9p,sharename=/ \
-s 30,xhci,tablet \
-s 31,lpc \
-l bootrom,/usr/local/share/uefi-firmware/BHYVE_UEFI_CODE.fd \
vm0:20 < /dev/null & sleep 2 && vncviewer 0:20

The installer is not able to start the installation of Ubuntu. I would like to know the reason(s).

PS :

lspci on FreeBSD :

00:00.0 Host bridge: Intel Corporation 8th/9th Gen Core 8-core Desktop Processor Host Bridge/DRAM Registers [Coffee Lake S] (rev 0d)
00:01.0 PCI bridge: Intel Corporation 6th-10th Gen Core Processor PCIe Controller (x16) (rev 0d)
00:01.1 PCI bridge: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor PCIe Controller (x8) (rev 0d)
00:02.0 Display controller: Intel Corporation CoffeeLake-S GT2 [UHD Graphics 630] (rev 02)
00:12.0 Signal processing controller: Intel Corporation Cannon Lake PCH Thermal Controller (rev 10)
00:14.0 USB controller: Intel Corporation Cannon Lake PCH USB 3.1 xHCI Host Controller (rev 10)
00:14.2 RAM memory: Intel Corporation Cannon Lake PCH Shared SRAM (rev 10)
00:16.0 Communication controller: Intel Corporation Cannon Lake PCH HECI Controller (rev 10)
00:17.0 SATA controller: Intel Corporation Cannon Lake PCH SATA AHCI Controller (rev 10)
00:1b.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #17 (rev f0)
00:1c.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #1 (rev f0)
00:1d.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #9 (rev f0)
00:1f.0 ISA bridge: Intel Corporation Z390 Chipset LPC/eSPI Controller (rev 10)
00:1f.3 Audio device: Intel Corporation Cannon Lake PCH cAVS (rev 10)
00:1f.4 SMBus: Intel Corporation Cannon Lake PCH SMBus Controller (rev 10)
00:1f.5 Serial bus controller: Intel Corporation Cannon Lake PCH SPI Controller (rev 10)
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (7) I219-V (rev 10)
01:00.0 VGA compatible controller: NVIDIA Corporation GP106 [GeForce GTX 1060 3GB] (rev a1)
01:00.1 Audio device: NVIDIA Corporation GP106 High Definition Audio Controller (rev a1)
02:00.0 VGA compatible controller: NVIDIA Corporation TU102 [GeForce RTX 2080 Ti] (rev a1)
02:00.1 Audio device: NVIDIA Corporation TU102 High Definition Audio Controller (rev a1)
02:00.2 USB controller: NVIDIA Corporation TU102 USB 3.1 Host Controller (rev a1)
02:00.3 Serial bus controller: NVIDIA Corporation TU102 USB Type-C UCSI Controller (rev a1)
03:00.0 Non-Volatile memory controller: Micron/Crucial Technology Device 5403 (rev 03)

lspci on ubuntu 22.10 :

00:00.0 Host bridge: Network Appliance Corporation Device 1275
00:01.0 Non-Volatile memory controller: Device fb5d:0a0a
00:02.0 SCSI storage controller: Red Hat, Inc. Virtio block device
00:03.0 SCSI storage controller: Red Hat, Inc. Virtio block device
00:04.0 SCSI storage controller: Red Hat, Inc. Virtio block device
00:06.0 VGA compatible controller: Device fb5d:40fb
00:07.0 Display controller: Intel Corporation CoffeeLake-S GT2 [UHD Graphics 630] (rev 02)
00:08.0 VGA compatible controller: NVIDIA Corporation TU102 [GeForce RTX 2080 Ti] (rev a1)
00:08.1 Audio device: NVIDIA Corporation TU102 High Definition Audio Controller (rev a1)
00:08.2 USB controller: NVIDIA Corporation TU102 USB 3.1 Host Controller (rev a1)
08:00.3 Serial bus controller: NVIDIA Corporation TU102 USB Type-C UCSI Controller (rev a1)
00:0a.0 Ethernet controller: Red Hat, Inc. Virtio network device
00:0b.0 SCSI storage controller: Red Hat, Inc. Virtio filesystem
00:0c.0 Audio device: Intel Corporation NM10/ICH7 Family High Definition Audio Controller
00:1e.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller
00:1f.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]

 

[ZioMario]

A reddit user says :

My friend, you are delving into the deep magic, and the answer is "yes and no".
The igpu will throw out a (actually probably 2) framebuffer(s) in some format in it's memory space. You could try to figure out what their address is, then mmap that into the host and pull it that way.
After that you get to look through the prime/optimus code to see how they do the nv->igpu fb blit.
Alternately, you can render it completely in linux, but render to a PBO, then figure out how to marshall that to your host, some kind of exotic shared memory system or something.
My point is, this is very dark spellcraft, but probably not impossible, I just wouldn't do it unless I had to.