From: boris.ostrovsky@oracle.com
To: Anchal Agarwal <anchalag@amazon.com>
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, x86@kernel.org, jgross@suse.com,
linux-pm@vger.kernel.org, linux-mm@kvack.org, kamatam@amazon.com,
sstabellini@kernel.org, konrad.wilk@oracle.com,
roger.pau@citrix.com, axboe@kernel.dk, davem@davemloft.net,
rjw@rjwysocki.net, len.brown@intel.com, pavel@ucw.cz,
peterz@infradead.org, eduval@amazon.com, sblbir@amazon.com,
xen-devel@lists.xenproject.org, vkuznets@redhat.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
dwmw@amazon.co.uk, benh@kernel.crashing.org
Subject: Re: [PATCH v3 01/11] xen/manage: keep track of the on-going suspend mode
Date: Tue, 15 Sep 2020 15:58:45 -0400 [thread overview]
Message-ID: <5f1e4772-7bd9-e6c0-3fe6-eef98bb72bd8@oracle.com> (raw)
In-Reply-To: <20200915180055.GB19975@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>
>>
>>
>>>>> +
>>>>> +static int xen_setup_pm_notifier(void)
>>>>> +{
>>>>> + if (!xen_hvm_domain() || xen_initial_domain())
>>>>> + return -ENODEV;
>>>>
>>>> I don't think this works anymore.
>>> What do you mean?
>>> The first check is for xen domain types and other is for architecture support.
>>> The reason I put this check here is because I wanted to segregate the two.
>>> I do not want to register this notifier at all for !hmv guest and also if its
>>> an initial control domain.
>>> The arm check only lands in notifier because once hibernate() api is called ->
>>> calls pm_notifier_call_chain for PM_HIBERNATION_PREPARE this will fail for
>>> aarch64.
>>> Once we have support for aarch64 this notifier can go away altogether.
>>>
>>> Is there any other reason I may be missing why we should move this check to
>>> notifier?
>>
>>
>> Not registering this notifier is equivalent to having it return NOTIFY_OK.
>>
> How is that different from current behavior?
>>
>> In your earlier versions just returning NOTIFY_OK was not sufficient for
>> hibernation to proceed since the notifier would also need to set
>> suspend_mode appropriately. But now your notifier essentially filters
>> out unsupported configurations. And so if it is not called your
>> configuration (e.g. PV domain) will be considered supported.
>>
> I am sorry if I am having a bit of hard time understanding this.
> How will it be considered supported when its not even registered? My
> understanding is if its not registered, it will not land in notifier call chain
> which is invoked in pm_notifier_call_chain().
Returning an error from xen_setup_pm_notifier() doesn't have any effect
on whether hibernation will start. It's the notifier that can stop it.
>
> As Roger, mentioned in last series none of this should be a part of PVH dom0
> hibernation as its not tested but this series should also not break anything.
> If I register this notifier for PVH dom0 and return error later that will alter
> the current behavior right?
>
> If a pm_notifier for pvh dom0 is not registered then it will not land in the
> notifier call chain and system will work as before this series.
> If I look for unsupported configurations, then !hvm domain is also one but we
> filter that out at the beginning and don't even bother about it.
>
> Unless you mean guest running VMs itself? [Trying to read between the lines may
> not be the case though]
In hibernate():
error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1,
&nr_calls);
if (error) {
nr_calls--;
goto Exit;
}
Is you don't have notifier registered (as will be the case with PV
domains and dom0) you won't get an error and proceed with hibernation.
(And now I actually suspect it didn't work even with your previous patches)
But something like this I think will do what you want:
static int xen_pm_notifier(struct notifier_block *notifier,
unsigned long pm_event, void *unused)
{
if (IS_ENABLED(CONFIG_ARM64) ||
!xen_hvm_domain() || xen_initial_domain() ||
(pm_event == PM_SUSPEND_PREPARE)) {
if ((pm_event == PM_SUSPEND_PREPARE) || (pm_event ==
PM_HIBERNATION_PREPARE))
pr_warn("%s is not supported for this guest",
(pm_event == PM_SUSPEND_PREPARE) ?
"Suspend" : "Hibernation");
return NOTIFY_BAD;
return NOTIFY_OK;
}
static int xen_setup_pm_notifier(void)
{
return register_pm_notifier(&xen_pm_notifier_block);
}
I tried to see if there is a way to prevent hibernation without using
notifiers (like having a global flag or something) but didn't find
anything obvious. Perhaps others can point to a simpler way of doing this.
-boris
next prev parent reply other threads:[~2020-09-15 20:03 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 22:22 [PATCH v3 00/11] Fix PM hibernation in Xen guests Anchal Agarwal
2020-08-21 22:25 ` [PATCH v3 01/11] xen/manage: keep track of the on-going suspend mode Anchal Agarwal
2020-09-13 15:43 ` boris.ostrovsky
2020-09-14 21:47 ` Anchal Agarwal
2020-09-15 0:24 ` boris.ostrovsky
2020-09-15 18:00 ` Anchal Agarwal
2020-09-15 19:58 ` boris.ostrovsky [this message]
2020-09-21 21:54 ` Anchal Agarwal
2020-09-22 16:18 ` boris.ostrovsky
2020-09-22 23:17 ` Anchal Agarwal
[not found] ` <20200925190423.GA31885@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>
2020-09-25 20:02 ` boris.ostrovsky
2020-09-25 22:28 ` Anchal Agarwal
2020-09-28 18:49 ` boris.ostrovsky
2020-09-30 21:29 ` Anchal Agarwal
2020-10-01 12:43 ` boris.ostrovsky
2021-05-21 5:26 ` Anchal Agarwal
2021-05-25 22:23 ` Boris Ostrovsky
2021-05-26 4:40 ` Anchal Agarwal
2021-05-26 18:29 ` Boris Ostrovsky
[not found] ` <20210528215008.GA19622@dev-dsk-anchalag-2a-9c2d1d96.us-west-2.amazon.com>
2021-06-01 14:18 ` Boris Ostrovsky
2021-06-02 19:37 ` Anchal Agarwal
2021-06-03 20:11 ` Boris Ostrovsky
2021-06-03 23:27 ` Anchal Agarwal
2021-06-04 1:49 ` Boris Ostrovsky
2020-09-13 17:07 ` boris.ostrovsky
2020-08-21 22:26 ` [PATCH v3 02/11] xenbus: add freeze/thaw/restore callbacks support Anchal Agarwal
2020-09-13 16:11 ` boris.ostrovsky
2020-09-15 19:56 ` Anchal Agarwal
2020-08-21 22:26 ` [PATCH v3 03/11] x86/xen: Introduce new function to map HYPERVISOR_shared_info on Resume Anchal Agarwal
2020-08-21 22:27 ` [PATCH v3 04/11] x86/xen: add system core suspend and resume callbacks Anchal Agarwal
2020-09-13 17:25 ` boris.ostrovsky
2020-08-21 22:27 ` [PATCH v3 05/11] genirq: Shutdown irq chips in suspend/resume during hibernation Thomas Gleixner
2020-08-22 0:36 ` Thomas Gleixner
2020-08-24 17:25 ` Anchal Agarwal
2020-08-25 13:20 ` Christoph Hellwig
2020-08-25 15:25 ` Thomas Gleixner
2020-08-21 22:28 ` [PATCH v3 06/11] xen-blkfront: add callbacks for PM suspend and hibernation Anchal Agarwal
2020-08-21 22:29 ` [PATCH v3 07/11] xen-netfront: " Anchal Agarwal
2020-08-21 22:29 ` [PATCH v3 08/11] x86/xen: save and restore steal clock during PM hibernation Anchal Agarwal
2020-08-21 22:30 ` [PATCH v3 09/11] xen: Introduce wrapper for save/restore sched clock offset Anchal Agarwal
2020-08-21 22:30 ` [PATCH v3 10/11] xen: Update sched clock offset to avoid system instability in hibernation Anchal Agarwal
2020-09-13 17:52 ` boris.ostrovsky
2020-08-21 22:31 ` [PATCH v3 11/11] PM / hibernate: update the resume offset on SNAPSHOT_SET_SWAP_AREA Anchal Agarwal
2020-08-28 18:26 ` [PATCH v3 00/11] Fix PM hibernation in Xen guests Anchal Agarwal
2020-08-28 18:29 ` Rafael J. Wysocki
2020-08-28 18:39 ` Anchal Agarwal
2020-09-11 20:44 ` Anchal Agarwal
2020-09-11 15:19 ` boris.ostrovsky
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