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
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