On Wed, Apr 10, 2013 at 09:20:52AM -0600, Alex Williamson wrote:
> On Wed, 2013-04-10 at 12:01 +0300, Gleb Natapov wrote:
> > On Tue, Apr 09, 2013 at 04:17:48PM -0600, Alex Williamson wrote:
> > > On Tue, 2013-04-09 at 11:18 -0600, Alex Williamson wrote:
> > > > On Tue, 2013-04-09 at 08:22 -0400, de...@lavabit.com wrote:
> > > > > Hi!
> > > > >
> > > > > I've tried passing through my ASUS Radeon HD7750, but qemu just hogs
> > > > > 100%
> > > > > of one core and stops. Since the display didn't light up, I couldn't
> > > > > see
> > > > > how far Win 7 boot went. For a Linux guest I tried redirecting kernel
> > > > > messages to serial console, but there was nothing (qemu stops even
> > > > > before
> > > > > kernel start?).
> > > > >
> > > > > Also, this GPU is kinda troublesome: it doesn't work with the
> > > > > proprietary
> > > > > driver if VT-d is enabled in BIOS (boot process stops with "dmar:
> > > > > DRHD:
> > > > > handling fault status reg 3"). The GPU works with the FOSS driver,
> > > > > though.
> > > > > Could this somehow be related to the passthrough issue?
> > > > >
> > > > > Anyway, VT-d in pci-assign mode works for network adapters on this
> > > > > host.
> > > > > It runs kernel 3.9.0-rc5 (with vfio-vga enabled), qemu git from
> > > > > yesterday,
> > > > > and seabios 1.7.2. The host has no driver installed for the GPU.
> > > > > Before
> > > > > assiging it to qemu I'd run "echo '1002 683f' >
> > > > > /sys/bus/pci/drivers/vfio-pci/new_id" and the same for the associated
> > > > > HDMI
> > > > > device. Command line:
> > > > > qemu-kvm -machine q35,accel=kvm \
> > > > > -cpu host -smp 4 -m 2G \
> > > > > -vga none -display none \
> > > > > -kernel /kvm/kernel-3.7.8 -append 'root=/dev/vda
> > > > > console=ttyS0' \
> > > > > -drive
> > > > > index=0,media=disk,cache=none,if=virtio,aio=native,file=/dev/vg3/gpu \
> > > > > -device vfio-pci,host=01:00.0,x-vga=on \
> > > > > -device vfio-pci,host=01:00.1 \
> > > > > -serial telnet:127.0.0.1:52990,server
> > > >
> > > > You should always at least get monitor sync if it's going to work, but
> > > > you may have to reboot the host between each attempt. I've been doing
> > > > most of the VGA development on an AMD box and swapping over to an Intel
> > > > system reminds me why. Try removing the ",accel=kvm -cpu host -smp 4"
> > > > pieces of your command an try again. If that works, it means there are
> > > > still broken bits of real mode handling in KVM. My HD7850 hangs on an
> > > > Intel host the same way you describe, but posts if I disable KVM
> > > > support. Thanks,
> > >
> > > Gleb,
> > >
> > > If I run trace-cmd while I'm in this hung state with KVM enabled, the
> > > log is filled with:
> > >
> > > qemu-system-x86-9569 [000] 10027.806836: kvm_emulate_insn:
> > > c0000:b2d3: ff 7d 00
> > >
> > > I hope this means more to you than it does to me ;) Based on the
> > > segment register we're executing in the VGA BIOS for the assigned VGA
> > > device. Let me know what more I can provide to help debug. Thanks,
> > >
> > This is wrong encoding. Such instruction does not exists. Can you see
> > what happens before this emulation starts to happen.
>
> Yeah, it seems like b2d3 is a bad offset, if I align the code at d2 or
> d0 gdb is able to disassemble it. I'm not having much luck with
> breakpoints or stepping, but I'll keep fiddling with it to try to figure
> out how we're getting here. Thanks,
>
Able to disassemble and produce code that make sense? :)
--
Gleb.
