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, Alex
