[Qemu-devel] [BUG] Guest freezes when resuming from S3

[Luiz Capitulino <lcapitulino@redhat.com>]

Hi,

I won't have time to keep debugging this so I'll just report what I have.

The basic problem is: you suspend a Linux guest to RAM, and the screen
(or maybe the guest) freezes when resuming. Here's some debugging info:

v1.6.0: last fully working version
v1.7.0: doesn't exactly freeze, but the kernel prints an ACPI Error in a loop
        making the guest unusable (happens on resume)
v2.0.0: same as v1.7.0
v2.1.0: screen/guest freezes on resume, which is the current symptom and also
        happens on master (HEAD c47c61be8)

This is the ACPI error v1.7.0 and v2.0.0 print in a loop:

  ACPI Error: No installed handler for fixed event - SleepButton (3), disabling (20140724/evevent-286)

I bisected this considering the current symptom and the ACPI error as
being the same issue (that is, I'd consider both as "git bisect bad") and
bisect yields the following commit:

commit c046e8c4a26c902ca1b4f5bdf668a2da6bc75f54
Author: Michael S. Tsirkin <mst@redhat.com>
Date:   Wed Sep 11 13:33:31 2013 +0300

    piix4: disable io on reset

On the hand, testing the commit before this one works and that one doesn't.
But I've tried reverting that one on current master and that did not fix
the problem.