From: Claudio Fontana <cfontana@suse.de>
To: Cornelia Huck <cohuck@redhat.com>
Cc: "Laurent Vivier" <lvivier@redhat.com>,
"Peter Maydell" <peter.maydell@linaro.org>,
"Thomas Huth" <thuth@redhat.com>,
"Jason J. Herne" <jjherne@linux.ibm.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Marcelo Tosatti" <mtosatti@redhat.com>,
"Markus Armbruster" <armbru@redhat.com>,
qemu-devel@nongnu.org, "Roman Bolshakov" <r.bolshakov@yadro.com>,
"Wenchao Wang" <wenchao.wang@intel.com>,
haxm-team@intel.com, "Colin Xu" <colin.xu@intel.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Sunil Muthuswamy" <sunilmut@microsoft.com>,
"Richard Henderson" <rth@twiddle.net>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Eduardo Habkost" <ehabkost@redhat.com>
Subject: Re: [PATCH 3/3] cpu-timers, icount: new modules
Date: Fri, 10 Jul 2020 21:20:08 +0200 [thread overview]
Message-ID: <eb8e29c7-4cb5-8273-1c94-e62ea9e06485@suse.de> (raw)
In-Reply-To: <20200710083356.4c6e9f78.cohuck@redhat.com>
On 7/10/20 8:33 AM, Cornelia Huck wrote:
> On Thu, 9 Jul 2020 20:46:56 +0200
> Claudio Fontana <cfontana@suse.de> wrote:
>
>> 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?
>
> I don't see anything that would deal with icount here. Adding Jason to
> cc: in case he has an idea. (I assume it would behave the same under
> KVM, as the only thing different are the internal callbacks.)
yes, same between tcg and kvm.
>
>>
>>
>>>
>>> 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).
>
> Yes, I don't really see why skeys is so special. No endianness stuff, I
> assume?
No, does not seem to be the issue.
I discovered a way simpler way to "fix" it:
static bool icount_state_needed(void *opaque)
{
return 1;
}
Ie, making sure that the state is always saved/restored, even when unused.
Really weird.
I logged/debugged the vmstate code, and I can see that things seem symmetric between save and load when it comes to timers.
something puts 0s into the key somehow...
>
>>>
>>> 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
>>>>
>>>>
>>>
>>>
>>
>
>
next prev parent reply other threads:[~2020-07-10 19:21 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-29 9:35 [PATCH 0/3] QEMU cpus.c refactoring part1 Claudio Fontana
2020-06-29 9:35 ` [PATCH 1/3] softmmu: move softmmu only files from root Claudio Fontana
2020-07-03 17:21 ` Paolo Bonzini
2020-06-29 9:35 ` [PATCH 2/3] cpu-throttle: new module, extracted from cpus.c Claudio Fontana
2020-06-29 9:35 ` [PATCH 3/3] cpu-timers, icount: new modules Claudio Fontana
2020-07-08 14:34 ` Paolo Bonzini
2020-07-08 15:00 ` Claudio Fontana
2020-07-08 15:05 ` Paolo Bonzini
2020-07-08 15:07 ` Thomas Huth
2020-07-08 15:12 ` Paolo Bonzini
2020-07-08 15:15 ` Claudio Fontana
2020-07-08 15:15 ` Thomas Huth
2020-07-08 15:17 ` Claudio Fontana
2020-07-08 15:23 ` Paolo Bonzini
2020-07-08 15:30 ` Claudio Fontana
2020-07-09 18:38 ` Claudio Fontana
2020-07-09 18:46 ` Claudio Fontana
2020-07-10 6:33 ` Cornelia Huck
2020-07-10 19:20 ` Claudio Fontana [this message]
2020-07-13 10:46 ` Cornelia Huck
2020-07-11 11:40 ` Claudio Fontana
2020-07-13 10:51 ` Cornelia Huck
2020-07-13 11:27 ` Claudio Fontana
2020-07-10 4:36 ` Thomas Huth
2020-07-10 22:45 ` Paolo Bonzini
2020-07-11 9:14 ` Claudio Fontana
2020-07-11 9:39 ` Paolo Bonzini
2020-07-11 11:49 ` Claudio Fontana
2020-07-11 12:19 ` Paolo Bonzini
2020-07-11 12:48 ` Claudio Fontana
2020-07-29 8:48 ` Claudio Fontana
2020-07-29 10:01 ` Paolo Bonzini
2020-07-30 16:33 ` Claudio Fontana
2020-07-30 22:09 ` Paolo Bonzini
2020-07-31 10:59 ` Claudio Fontana
2020-07-02 6:27 ` [PATCH 0/3] QEMU cpus.c refactoring part1 Claudio Fontana
2020-07-03 17:21 ` Paolo Bonzini
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