[Xen-devel] Re: Question about Xen S3 and resume code - Linux dom0 never exits the xen_safe_halt hypercall after resume

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

> ideally ACPI S3/S5 has nothing to do with ACPI processor driver which is for 
> Cx/Px.

Right..
> 
> > 
> > (which is in the devel/acpi-s3.v0 branch).
> > 
> > the hypervisor, after an S3 resume sits forever in the default_idle. The
> > Linux dom0 is stuck looping (I think) around SCHEDOP_block hypercall.
> > 
> > http://darnok.org/xen/devel.acpi-s3.v1.serial.log
> > 
> > If that patch above is present and I've cpufreq=xen on the Xen
> > hypervisor then Linux kernel gets unstuck and returns to userspace:
> > 
> > http://darnok.org/xen/devel.acpi-s3.v0.serial.log
> 
> Compare your logs, the major difference is:
> 
> [  168.754739] calling  i2c-8+ @ 3096
> [  168.758200] call i2c-8+ returned 0 after 0 usecs
> <<< 1st case stuck here
> [  168.762882] calling  card0-VGA-1+ @ 3096
> [  168.766867] call card0-VGA-1+ returned 0 after 0 usecs
> [  168.772085] calling  ttm+ @ 3096
> [  168.775360] call ttm+ returned 0 after 0 usecs
> [  168.779870] PM: resume of devices complete after 13117.603 msecs
> [  168.786006] PM: Finishing wakeup.
> <<<2nd case forward progress
> 
> It looks that VGA card resume has some problem on resume, which then

In both cases - with the patch and without..

> makes dom0 stay in idle loop and thus block hypercall, and then due to
> no runnable vcpu so Xen most time in idle_loop too. In earlier log there're
> some stack trace in i915 driver. Perhaps you can try a different machine

Or remove the i915 just to eliminate that.
> or try native S3 on same box to make sure it's not mixed with native issues.
> 
> > 
> > (however, if I set cpuidle=0 cpufreq=none on the hypervisor line and
> > have the 9f301b0a0081676dfc71b7f0898295e6bcba391a patch it still
> > gets stuck).
> > 
> > I figured that the primary reason the guest is allowed to
> > exit is SCHEDOP_block loop is b/c the pm_idle call is set to the
> > acp_processor_idle which does "something" extra after the machine comes
> > out of a S3 suspend.
> 
> If that's the case I think you should disable CONFIG_ACPI_PROCESSOR in dom0
> before incorporating Xen specific version (the patch you tried). We don't want
> dom0 to play with Cx directly b/c it's the responsibility of Xen.

Huh? You misunderstood me. The 'acpi_processor_idle' is the hypervisor's
idle loop. It can be running inside of that one, or the 'default_idle' loop. 
Hence
my question why would that specific hypervisor idle loop make dom0 run nicely
while the default one would not.

In dom0, irregardless of the patches, the 'default_idle' is run which makes the
xen_safe_halt paravirt call.

> 
> Of course we still need figure out why same issues occur with cpuidle=0/
> cpufreq=none, which however can be revisited after the basic S3 works. :-)

Right. The end result of those parameters is that the 'default_idle' in the
hypervisor is choosen instead of the 'acpi_processor_idle' one.
> 
> > 
> > Any ideas?
> 
> No other ideas for now. From historical view Xen S3 was supported before

Hmm, I am actually tempted to start commenting out code in the 
acpi_processor_idle
and seeing what will cause it to have the same failure as 'default_idle'.


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