If I set rombar=off in the hostdev section of libvirt xml, sometimes the instance can run normally with output to the screen.

Can seabios run without any vga rom?

But sometimes there will be kernel kvm exception:

KVM internal error. Suberror: 1

emulation failure

RAX=0000000000000001 RBX=ffff950196c27780 RCX=ffff950196c27780 RDX=fffff80e9ca51ad0

RSI=fffff800a221bbc0 RDI=fffff800a2215180 RBP=fffff800a4239600 RSP=fffff800a4248f10

R8 =ffff950196c27780 R9 =ffff950196c27760 R10=0000000000000002 R11=0000000000000000

R12=0000000000f84f43 R13=00000000ffffffff R14=ffff950196db8180 R15=fffff800a2409000

RIP=fffff80e9ca51af2 RFL=00010202 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0

ES =002b 0000000000000000 ffffffff 00c0f300 DPL=3 DS [-WA]

CS =0010 0000000000000000 00000000 00209b00 DPL=0 CS64 [-RA]

SS =0018 0000000000000000 00000000 00409300 DPL=0 DS [-WA]

DS =002b 0000000000000000 ffffffff 00c0f300 DPL=3 DS [-WA]

FS =0053 0000000000000000 00003c00 0040f300 DPL=3 DS [-WA]

GS =002b fffff800a2215000 ffffffff 00c0f300 DPL=3 DS [-WA]

LDT=0000 0000000000000000 ffffffff 00c00000

TR =0040 fffff800a422f000 00000067 00008b00 DPL=0 TSS64-busy

GDT= fffff800a4230fb0 00000057

IDT= fffff800a422e000 00000fff

CR0=80050031 CR2=ffffa68866c97000 CR3=00000000001aa000 CR4=001506f8

DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000

DR6=00000000ffff0ff0 DR7=0000000000000400

EFER=0000000000000d01

Code=c1 01 83 f8 01 74 1c 8b 41 04 85 c0 74 0d 0f 1f 40 00 f3 90 <8b> 41 04 85 c0 75 f7 33 c0 48 83 c4 20 5b c3 48 8b 41 08 48 8b 51 18 48 8b 49 10 ff 15 fd

Kevin O'Connor <kevin@koconnor.net> 于2018年10月19日周五上午7:20写道：

On Sun, Oct 14, 2018 at 03:32:22PM +0800, Acewind wrote:
> Dear All,
> These days I'm working on Intel IGD passthrough by qemu+vfio.
> Success on i3-6100, but failed on i3-6100U.
[...]
> Found 2 cpu(s) max supported 2 cpu(s)
> Copying PIR from 0x7ffbfca0 to 0x000f1c40
> Copying MPTABLE from 0x00006e90/7ffa8e80 to 0x000f1b10
> Copying SMBIOS entry point from 0x00006e90 to 0x000f1930
> Scan for VGA option rom
> Running option rom at c000:0003
>
> Now seabios stops and monitor shows no signal.
> I have install win10 directly on the host and it works well. Does it means
> the vga rom image is ok? What can I do for further debug? Thanks!

The "Running option rom at c000:0003" indicates a video card option
rom was found and SeaBIOS started executing it. The likely reason for
the failure is that the video option rom itself crashed. It's
difficult to debug these types of failures because it is rare to have
access to the video rom code.

-Kevin