[PATCH v3 00/10] pci: fix unhandled interrupt on shutdown

["Michael S. Tsirkin" <mst@redhat.com>]

Fam Zheng noticed that pci shutdown disables msi and msix of a device while
device is still active. This was intended to fix kexec with fusion devices but
had the unintended effect of breaking even regular shutdown when using virtio.

As a result, people reported VMs being hung on shutdown,
with traces that look like this:

...

  [<ffffffff815f367b>] ? _raw_spin_unlock_irqrestore+0x1b/0x40
  [<ffffffff812e068f>] pci_bus_read_config_word+0x9f/0xb0
  [<ffffffff812e205c>] pci_read_config_word+0x1c/0x20
  [<ffffffff812e5ea3>] pci_intx+0x33/0xb0
  [<ffffffff81304ddd>] pci_msix_shutdown+0x8d/0x90
  [<ffffffff812ead26>] pci_device_shutdown+0x46/0x60
  [<ffffffff813b4258>] device_shutdown+0xc8/0x180
  [<ffffffff810761c5>] kernel_power_off+0x35/0x80
  [<ffffffff81077ceb>] SYSC_reboot+0x18b/0x260
  [<ffffffff811c5bb5>] ? d_free+0x55/0x60
  [<ffffffff811cf414>] ? mntput+0x24/0x40
  [<ffffffff811b1613>] ? __fput+0x183/0x270
  [<ffffffff81077dee>] SyS_reboot+0xe/0x10
  [<ffffffff815fc819>] system_call_fastpath+0x16/0x1b

...

as well as the messages that look like this:
BUG: soft lockup - CPU#2 stuck for 22s!  [poweroff:1964]

The same problem would affect any driver which doesn't register
a level interrupt handler when using msix.

I think the fix is to avoid touching device on shutdown:
we clear bus master anyway, so we won't get any more
msi interrupts, and bus reset will clear the msi/msix
state eventually.

The patch that added the code in question is from
	d52877c7b1afb8c37ebe17e2005040b79cb618b0:
        "pci/irq: let pci_device_shutdown to call pci_msi_shutdown v2"
from 2008, but it turns out that in 2011 the following commit
    commit d5dea7d95c48d7bc951cee4910a7fd9c0cd26fb0
        "PCI: msi: Disable msi interrupts when we initialize a pci device"
fixed the issue in a more robust way.  The only thing left to do is to
fix configurations with CONFIG_PCI_MSI disabled, and then
d52877c7b1afb8c37ebe17e2005040b79cb618b0 can be reverted.

Status:

Patches 1-6 work well for me.
Given they affect all pci devices, and the bug has been there since 2.6 times,
I think there's no rush: we can merge them for 4.1.

At the same time, once merged, patches 1-4 will likely make a good stable
candidate.

Patches 7-10 compiled only, will need maintainer ack.

Please review, and consider at least 1-6 for 4.1.

Changes from v3:
	move code from probe to device enumeration
	add patches to unexport pci_msi_off

Michael S. Tsirkin (10):
  pci: export functions for msi/msix ctrl
  pci: move pci_msi_init_pci_dev to pci.c
  pci: drop some duplicate code
  pci: don't disable msi/msix at shutdown
  pci: make msi/msix shutdown functions static
  virtio_pci: drop msi_off on probe
  ntb: drop pci_msi_off call on probe
  mic: drop pci_msi_off call on probe
  pci: drop pci_msi_off calls from quirks
  pci: unexport pci_msi_off

 drivers/pci/pci.h                  | 25 +++++++++++++--
 include/linux/pci.h                |  5 ---
 drivers/misc/mic/host/mic_intr.c   |  2 --
 drivers/ntb/ntb_hw.c               |  2 --
 drivers/pci/msi.c                  | 62 ++++++++------------------------------
 drivers/pci/pci-driver.c           |  2 --
 drivers/pci/pci.c                  | 26 ++++------------
 drivers/pci/probe.c                | 16 ++++++++++
 drivers/pci/quirks.c               |  2 --
 drivers/virtio/virtio_pci_common.c |  3 --
 10 files changed, 57 insertions(+), 88 deletions(-)

-- 
MST