Re: [PATCH 3/3] cpu-timers, icount: new modules

[Claudio Fontana]

On 7/9/20 8:38 PM, Claudio Fontana wrote:
> On 7/8/20 5:05 PM, Paolo Bonzini wrote:
>> On 08/07/20 17:00, Claudio Fontana wrote:
>>>> Bisectable, 100% failure rate, etc. :(  Can you split the patch in
>>>> multiple parts, specifically separating any rename or introducing of
>>>> includes from the final file move?
>>> Hi Paolo,
>>>
>>> will take a look!
>>>
>>> Is this captured by some travis / cirrus-ci / anything I can easily see the 
>>> result of?
>>>
>>>
>>
>> Nope, unfortunately we don't have an s390 CI.  But if you can get your
>> hands on one, just "./configure --target-list=s390x-softmmu && make &&
>> make check-block" will show it.
> 
> So this is tricky, but I am making some progress after getting my hands on 
> one.
> Maybe if someone understands s390 keys better, I could be clued in.


Also adding Cornelia to Cc:.

Maybe the savevm_s390_storage_keys SaveVMHandlers etc assume that the icount 
state part of the vmstate is there?


> 
> In short this goes away if I again set icount to enabled for qtest,
> basically ensuring that --enable-tcg is there and then reenabling icount.
> 
> qtest was forcing icount and shift=0 by creating qemu options, in order to 
> misuse its counter feature,
> instead of using a separate counter.
> 
> Removing that ugliness we end up with different behavior of save/load, 
> because vmstate will now suddenly not contain icount-related values anymore.
> What I do not understand is why this causes a problem because save should 
> just not store the icount state and load should just not load the icount 
> state,
> and why we die on the load of s390 keys state (it works just fine for other 
> architectures).
> 
> Here is a diff that makes the problem disappear, but needs --enable-tcg:
> 
> 
> ----------------------------------------------------------------------------------------------------
> diff --git a/accel/qtest.c b/accel/qtest.c
> index 119d0f16a4..4cb16abc2c 100644
> --- a/accel/qtest.c
> +++ b/accel/qtest.c
> @@ -23,6 +23,12 @@
>  
>  static int qtest_init_accel(MachineState *ms)
>  {
> +    QemuOpts *opts = qemu_opts_create(qemu_find_opts("icount"), NULL, 0,
> +                                      &error_abort);
> +    qemu_opt_set(opts, "shift", "0", &error_abort);
> +    icount_configure(opts, &error_abort);
> +    qemu_opts_del(opts);
> +
>      return 0;
>  }
>  
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index f39fd5270b..a5e788c86a 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2786,10 +2786,12 @@ static void configure_accelerators(const char 
> *progname)
>          error_report("falling back to %s", ac->name);
>      }
>  
> +    /*
>      if (icount_enabled() && !tcg_enabled()) {
>          error_report("-icount is not allowed with hardware virtualization");
>          exit(1);
>     }
> +    */
>  }
>  
>  static void create_default_memdev(MachineState *ms, const char *path)
> ----------------------------------------------------------------------------------------------------
> 
> Without this patch, here is the full failure, maybe someone has a good hint, 
> otherwise I'll keep digging from here inside the s390-specific code.
> 
> QA output created by 267
> 
> === No block devices at all ===
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing:
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> Error: No block device can accept snapshots
> (qemu) info snapshots
> No available block device supports snapshots
> (qemu) loadvm snap0
> Error: No block device supports snapshots
> (qemu) quit
> 
> 
> === -drive if=none ===
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -drive driver=file,file=TEST_DIR/t.IMGFMT,if=none
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> Error: Device 'none0' is writable but does not support snapshots
> (qemu) info snapshots
> No available block device supports snapshots
> (qemu) loadvm snap0
> Error: Device 'none0' is writable but does not support snapshots
> (qemu) quit
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -drive driver=IMGFMT,file=TEST_DIR/t.IMGFMT,if=none
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> (qemu) info snapshots
> List of snapshots present on all disks:
> ID        TAG                     VM SIZE                DATE       VM CLOCK
> --        snap0                      SIZE yyyy-mm-dd hh:mm:ss   00:00:00.000
> (qemu) loadvm snap0
> (qemu) quit
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -drive driver=IMGFMT,file=TEST_DIR/t.IMGFMT,if=none -device 
> virtio-blk,drive=none0
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> (qemu) info snapshots
> List of snapshots present on all disks:
> ID        TAG                     VM SIZE                DATE       VM CLOCK
> --        snap0                      SIZE yyyy-mm-dd hh:mm:ss   00:00:00.000
> (qemu) loadvm snap0
> (qemu) quit
> 
> 
> === -drive if=virtio ===
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -drive driver=file,file=TEST_DIR/t.IMGFMT,if=virtio
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> Error: Device 'virtio0' is writable but does not support snapshots
> (qemu) info snapshots
> No available block device supports snapshots
> (qemu) loadvm snap0
> Error: Device 'virtio0' is writable but does not support snapshots
> (qemu) quit
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -drive driver=IMGFMT,file=TEST_DIR/t.IMGFMT,if=virtio
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> (qemu) info snapshots
> List of snapshots present on all disks:
> ID        TAG                     VM SIZE                DATE       VM CLOCK
> --        snap0                      SIZE yyyy-mm-dd hh:mm:ss   00:00:00.000
> (qemu) loadvm snap0
> (qemu) quit
> 
> 
> === Simple -blockdev ===
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> Error: Device '' is writable but does not support snapshots
> (qemu) info snapshots
> No available block device supports snapshots
> (qemu) loadvm snap0
> Error: Device '' is writable but does not support snapshots
> (qemu) quit
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file 
> -blockdev driver=IMGFMT,file=file,node-name=fmt
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> (qemu) info snapshots
> List of snapshots present on all disks:
> ID        TAG                     VM SIZE                DATE       VM CLOCK
> --        snap0                      SIZE yyyy-mm-dd hh:mm:ss   00:00:00.000
> (qemu) loadvm snap0
> (qemu) quit
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file 
> -blockdev driver=raw,file=file,node-name=raw -blockdev 
> driver=IMGFMT,file=raw,node-name=fmt
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> (qemu) info snapshots
> List of snapshots present on all disks:
> ID        TAG                     VM SIZE                DATE       VM CLOCK
> --        snap0                      SIZE yyyy-mm-dd hh:mm:ss   00:00:00.000
> (qemu) loadvm snap0
> (qemu) quit
> 
> 
> === -blockdev with a filter on top ===
> 
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
> Testing: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file 
> -blockdev driver=IMGFMT,file=file,node-name=fmt -blockdev 
> driver=copy-on-read,file=fmt,node-name=filter
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> (qemu) info snapshots
> List of snapshots present on all disks:
> ID        TAG                     VM SIZE                DATE       VM CLOCK
> --        snap0                      SIZE yyyy-mm-dd hh:mm:ss   00:00:00.000
> (qemu) loadvm snap0
> (qemu) quit
> 
> 
> === -blockdev with a backing file ===
> 
> Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
> backing_file=TEST_DIR/t.IMGFMT.base
> Testing: -blockdev 
> driver=file,filename=TEST_DIR/t.IMGFMT.base,node-name=backing-file -blockdev 
> driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file -blockdev 
> driver=IMGFMT,file=file,backing=backing-file,node-name=fmt
> QEMU X.Y.Z monitor - type 'help' for more information
> (qemu) savevm snap0
> (qemu) info snapshots
> List of snapshots present on all disks:
> ID        TAG                     VM SIZE                DATE       VM CLOCK
> --        snap0                      SIZE yyyy-mm-dd hh:mm:ss   00:00:00.000
> (qemu) loadvm snap0
> Unexpected storage key flag data: 0
> error while loading state for instance 0x0 of device 's390-skeys'
> Error: Error -22 while loading VM state
> 
> 
> 
> 
>>
>>>>
>>>>    #if defined CONFIG_TCG || !defined NEED_CPU_H
>>>>    extern bool icount_enabled(void);
>>>>    #else
>>>>    #define icount_enabled() 0
>>>>    #endif
>>>>
>>>> (This way, more TCG-only code in cpus.c gets elided).  You can integrate
>>>> this change in the next version.
>>>>
>>>> Paolo
>>>>
>>>
>>> Weird, I tested with --disable-tcg explicitly (but may be some time ago 
>>> now, as I constantly rebased).
>>>
>>> Will take a look at the introduction of this #defines in place of variables,
>>> as this mechanisms will not work in the future for target-specific modules.
>>
>> This is only done for per-target files so it should not be a problem.
>>
>> Paolo
>>
>>
> 
>