Re: [Qemu-devel] [for-4.2 PATCH 0/6] Block-related record/replay fixes

[Pavel Dovgalyuk]

> From: Alex Bennée [mailto:address@hidden]
> Pavel Dovgalyuk <address@hidden> writes:
> 
> >> -----Original Message-----
> >> From: Alex Bennée [mailto:address@hidden]
> >> Sent: Tuesday, September 17, 2019 10:02 PM
> >> To: Pavel Dovgalyuk
> >> Cc: address@hidden; address@hidden; address@hidden;
> >> address@hidden; address@hidden; address@hidden;
> >> address@hidden; address@hidden; address@hidden; address@hidden;
> >> address@hidden; address@hidden; address@hidden; address@hidden;
> >> address@hidden; address@hidden; address@hidden;
> >> address@hidden; address@hidden; address@hidden
> >> Subject: Re: [for-4.2 PATCH 0/6] Block-related record/replay fixes
> >>
> >>
> >> Pavel Dovgalyuk <address@hidden> writes:
> >>
> >> > The set of patches include the block-related updates
> >> > of the record/replay icount feature:
> >> >  - application of 'snapshot' option on the file layer instead of
> >> >    the top one: command line and documentation fix
> >> >  - implementation of bdrv_snapshot_goto for blkreplay driver
> >> >  - start/stop fix in replay mode with attached block devices
> >> >  - record/replay of bh oneshot events, used in the block layer
> >>
> >> Can we come up with a reasonable smoke test to verify record/replay is
> >> functional? AIUI we don't need a full OS but we do need a block device
> >> to store the replay data. Could we use one of the simple system tests
> >> like "memory" and run that through a record and replay cycle?
> >
> > That's would be great.
> > I'm not familiar with testing framework and couldn't find "memory"
> > test that you refer to.
> 
> The memory test code is in tests/tcg/multiarch/system and gets combined
> with the boot code for whichever target can build it. For example on
> aarch64 it is run like:
> 
>   timeout 15  $BLD/aarch64-softmmu/qemu-system-aarch64 -monitor none -display 
> none -chardev
> file,path=memory.out,id=output  -M virt -cpu max -display none 
> -semihosting-config
> enable=on,target=native,chardev=output -kernel memory

Yes, rr testing could be that simple, but in full system emulation mode.
Simplest tests may be run even without the block devices:

qemu-system-aarch64 -monitor none -display none -chardev 
file,path=memory.out,id=output
-M virt -cpu max -kernel memory -net none -icount 
shift=5,rr=record,rrfile=record.bin

Better testing must include some block device like Linux boot image or 
something similar.

> The test binaries will be in $BLD/tests/tcg/aarch64-softmmu and are
> built when you run "make check-tcg" and have either the appropriate
> cross compilers installed on your system or docker enabled and setup
> (see docs/devel/testing.rst).
> 
> > Replay test must at least the following:
> > 1. record some execution
> > 2. replay that execution
> >
> > And there could be several endings:
> > 1. record stalled
> > 2. record crashed
> > 3. replay stalled
> > 4. replay crashed
> > 5. all executions finished successfully
> 
> If you can provide an appropriate set of invocations I can plumb them
> into the Makefiles for you.

That will be great, thank you.

Pavel Dovgalyuk