Re: [Qemu-devel] VM can not boot after commit 235e898

[Paolo Bonzini]

Il 24/07/2013 11:58, Alexander Graf ha scritto:
>> > No QEMU or kvm crashes, no error message printed, I mean it just hangs, 
>> > even no BIOS information are printed.
>> > And "top" shows QEMU consumes 100% cpu.
>> > 
>> > When I define DEBUG_KVM in kvm-all.c, and run QEMU(this time I boot a 
>> > normal OS disk), 
>> > # x86_64-softmmu/qemu-system-x86_64 -enable-kvm -hda 
>> > /mnt/nfs/Images/debian-append.img
>> > kvm_init_vcpu
>> > kvm_cpu_exec()
>> > handle_io
>> > handle_io
>> > handle_io
>> > handle_io
>> > 
>> > Only 4 debug messages(handle_io) are printed, then nothing is shown, and 
>> > "top" shows QEMU process uses 100% CPU.
> After this we're running in an endless loop of:
> 
>  qemu-system-x86-9298  [003] ...1 162090.918845: kvm_emulate_insn: 
> f0000:c489:66 ea 91 c4 0f 00 08 00 (prot16)
>  qemu-system-x86-9298  [003] d..2 162090.918846: kvm_entry: vcpu 0
> 
>   (qemu) x /i $pc
>   0x00000000000fc489:  ljmpl  $0x8,$0xfc491
> 
> With current master, qemu-system-x86_64 -enable-kvm is broken on at least 3.7 
> kernels (openSUSE 12.3).
> 
> Gleb, I don't remember all the glorious details of ljmpl, but would it have 
> to raise an MMIO request for a read-only memory slot which it fails to do?

The point of KVM_CAP_READONLY_MEM should be that it doesn't.

So, even without debugging it, I guess we need a KVM_CAP_READONLY_MEM2
or something like that.

Paolo