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Date: Wed, 13 Dec 2017 16:57:56 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Maarten Lankhorst <dev@mblankhorst.nl>
cc: Michal Hocko <mhocko@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Bjorn Helgaas <bhelgaas@google.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: Linux 4.15-rc2: Regression in resume from ACPI S3
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References: <CA+55aFxPBszFBt91KRNBrsQdJ10b+6fh9ySNzSKSX7JOq4WRPw@mail.gmail.com> <168050887.sZlTFXWCmO@aspire.rjw.lan> <CA+55aFwsMuHUBQz5kDNwRf17JnasXMWjvmLq5qXGH-694yeq1w@mail.gmail.com> <20171206121452.GA6320@dhcp22.suse.cz> <db81e89d-eee6-868c-dc10-c028f4c4be84@mblankhorst.nl>
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So I was finally able to figure out what the hell is going on:

Suspend:

 - The device suspend code puts the graphics card into a power
   state != PCI_D0.

 - Offline non boot CPUs

 - Break interrupt affinity. Allocate new vector on CPU 0, compose and
   write MSI message which ends up in:

   __pci_write_msi_msg(entry, msg)
   {
	if (dev->current_state != PCI_D0 || pci_dev_is_disconnected(dev)) {
	   /* Don't touch the hardware now */
	} else {
	   ....
	}
	entry->msg = *msg;
   }
 
  So because the device is not in PCI_D0 the message is not written. It's
  written in the device resume path.

Resume:
[  139.670446] ACPI: Low-level resume complete
[  139.670541] PM: Restoring platform NVS memory
[  139.672462] do_IRQ: 0.55 No irq handler for vector
[  139.672475] Enabling non-boot CPUs ...

So the spurious interrupt happens early and way before the device resume
code writes the new MSI message.

I checked the behaviour on 4.14. The MSI write is delayed there in the same
way, but there is no spurious interrupt. There is no interrupt coming in at
all _BEFORE_ the device is put out of PCI_D0.

And this has certainly nothing to do with the vector management changes,
but I can't figure yet what makes that spurious interrupt to be sent.

Any ideas welcome.

Thanks,

	tglx