Re: [Qemu-devel] [PATCH v3 00/11] MTTCG fix-ups for 2.9

[Pavel Dovgalyuk]

> From: Alex Bennée [mailto:address@hidden
> Pavel Dovgalyuk <address@hidden> writes:
> >> From: Alex Bennée [mailto:address@hidden
> >> Pavel Dovgalyuk <address@hidden> writes:
> >> >> From: address@hidden [mailto:mttcg-
> >> address@hidden
> >> >>
> >> >> The next thing on my list it to look at the icount problems and review
> >> >> Paolo's fixes for it. However those fixes should go in a separate
> >> >> series and I assume via Paolo's tree.
> >> >
> >> > Do you mean those problems that completely broke icount?
> >>
> >> Completely broke is a bit strong. Certainly I tested icount on my
> >> patches but I missed the pathological failure mode that led to the
> >> interaction between the BQL lock breaking patch and running a real
> >> guest. It didn't break icount so much as slow down guests so much they
> >> never got round to finishing their IRQ handling.
> >
> > That might look as slowing down in regular icount mode.
> > But it becomes non-deterministic in record/replay mode.
> > Therefore none of the recorded scenarios may be replayed.
> >
> > I tried the simplest command lines:
> >
> > qemu-system-i386.exe -icount shift=7,rr=record,rrfile=replay.bin -net
> > none
> 
> Running this against 2421f381dc (pre-merge of MTTCG) from the source
> tree generates no output. My command is on Linux:
> 
>   /x86_64-softmmu/qemu-system-x86_64 -icount 
> shift=7,rr=record,rrfile=replay.bin -net none
> 
> Do I need to specify the BIOS manually?

No, this command line works well for me. BIOS executes and shows some messages.
Do you have any graphical output for QEMU?

> > qemu-system-i386.exe -icount shift=7,rr=replay,rrfile=replay.bin -net none
> >
> > First one was used to record execution until BIOS will print its startup 
> > info.
> > The second one is for replay, but it can replay about 200000 instructions
> > until the problems with icount manifest itself - the execution does
> > not proceed.
> 
> What error message does it give? How do you know how many instructions
> have been executed?

It hangs after executing about 200000 instructions.
I checked -d exec logs.

> I ran the following test on both pre-mttcg-merge and my current HEAD
> which includes Paolo's fix series:
> 
>  ./arm-softmmu/qemu-system-arm -machine type=virt \
>     -display none -smp 1 -m 4096 -cpu cortex-a15 \
>     -kernel ../images/aarch32-current-linux-initrd-guest.img
>     -append "console=ttyAMA0" -serial mon:stdio \
>     -net none \
>     -icount shift=7,rr=record,rrfile=replay.bin
> 
> And then:
> 
>  ./arm-softmmu/qemu-system-arm -machine type=virt \
>     -display none -smp 1 -m 4096 -cpu cortex-a15 \
>     -kernel ../images/aarch32-current-linux-initrd-guest.img
>     -append "console=ttyAMA0" -serial mon:stdio \
>     -net none \
>     -icount shift=7,rr=replay,rrfile=replay.bin
> 
> And they both ran the same. However I kept running into:
> 
>  [    3.542408] RPC: Registered tcp NFSv4.1 backchannel transport module.
> qemu-system-arm: Missing character write event in the replay log
> 
> This seems to be a pre-existing

Does it mean that qemu-arm platform includes some serial devices that were
not detected by the replay?

Pavel Dovgalyuk