Passed through PCI device sometimes misbehave on Gen1 VMs when Hyper-V
DRM driver is also loaded. Looking at IOMEM assignment, we can see e.g.
$ cat /proc/iomem
...
f8000000-fffbffff : PCI Bus 0000:00
f8000000-fbffffff : 0000:00:08.0
f8000000-f8001fff : bb8c4f33-2ba2-4808-9f7f-02f3b4da22fe
...
fe0000000-fffffffff : PCI Bus 0000:00
fe0000000-fe07fffff : bb8c4f33-2ba2-4808-9f7f-02f3b4da22fe
fe0000000-fe07fffff : 2ba2:00:02.0
fe0000000-fe07fffff : mlx4_core
the interesting part is the 'f8000000' region as it is actually the
VM's framebuffer:
$ lspci -v
...
0000:00:08.0 VGA compatible controller: Microsoft Corporation Hyper-V virtual VGA (prog-if 00 [VGA controller])
Flags: bus master, fast devsel, latency 0, IRQ 11
Memory at f8000000 (32-bit, non-prefetchable) [size=64M]
...
hv_vmbus: registering driver hyperv_drm
hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] Synthvid Version major 3, minor 5
hyperv_drm 0000:00:08.0: vgaarb: deactivate vga console
hyperv_drm 0000:00:08.0: BAR 0: can't reserve [mem 0xf8000000-0xfbffffff]
hyperv_drm 5620e0c7-8062-4dce-aeb7-520c7ef76171: [drm] Cannot request framebuffer, boot fb still active?
Note: "Cannot request framebuffer" is not a fatal error in
hyperv_setup_gen1() as the code assumes there's some other framebuffer
device there but we actually have some other PCI device (mlx4 in this
case) config space there!
Resolve the issue by always reserving FB region on Gen1 VMs (PATCH3) and making
sure we never allocate anything besides framebuffer from there (PATCH4). PATCH1
is a preparatory change, PATCH2 fixes a loosely related issue in Hyper-V DRM
driver.
Vitaly Kuznetsov (4):
Drivers: hv: Move legacy Hyper-V PCI video device's ids to
linux/hyperv.h
drm/hyperv: Don't forget to put PCI device when removing conflicting
FB fails
Drivers: hv: Always reserve framebuffer region for Gen1 VMs
Drivers: hv: Never allocate anything besides framebuffer from
framebuffer memory region
drivers/gpu/drm/hyperv/hyperv_drm_drv.c | 5 +--
drivers/hv/vmbus_drv.c | 57 ++++++++++++++++++-------
drivers/video/fbdev/hyperv_fb.c | 4 --
include/linux/hyperv.h | 4 ++
4 files changed, 47 insertions(+), 23 deletions(-)
--
2.37.1
