linux/drivers/pci
Konrad Rzeszutek Wilk 098b1aeaf4 xen/pcifront: Deal with toolstack missing 'XenbusStateClosing' state.
There are two tool-stack that can instruct the Xen PCI frontend
and backend to change states: 'xm' (Python code with a daemon),
and 'xl' (C library - does not keep state changes).

With the 'xm', the path to disconnect a single PCI device (xm pci-detach
<guest> <BDF>) is:

4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected)->5(Closing*).

The * is for states that the tool-stack sets. For 'xl', it is similar:

4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected)

Both of them also tear down the XenBus structure, so the backend
state ends up going in the 3(Initialised) and calls pcifront_xenbus_remove.

When a PCI device is plugged back in (xm pci-attach <guest> <BDF>)
both of them follow the same pattern:

2(InitWait*), 3(Initialized*), 4(Connected*)->4(Connected).

[xen-pcifront ignores the 2,3 state changes and only acts when
4 (Connected) has been reached]

Note that this is for a _single_ PCI device. If there were two
PCI devices and only one was disconnected 'xm' would show the same
state changes.

The problem is that git commit 3d925320e9
("xen/pcifront: Use Xen-SWIOTLB when initting if required") introduced
a mechanism to initialize the SWIOTLB when the Xen PCI front moves to
Connected state. It also had some aggressive seatbelt code check that
would warn the user if one tried to change to Connected state without
hitting first the Closing state:

 pcifront pci-0: PCI frontend already installed!

However, that code can be relaxed and we can continue on working
even if the frontend is instructed to be the 'Connected' state with
no devices and then gets tickled to be in 'Connected' state again.

In other words, this 4(Connected)->5(Closing)->4(Connected) state
was expected, while 4(Connected)->.... anything but 5(Closing)->4(Connected)
was not. This patch removes that aggressive check and allows
Xen pcifront to work with the 'xl' toolstack (for one or more
PCI devices) and with 'xm' toolstack (for more than two PCI
devices).

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: stable@vger.kernel.org
[v2: Added in the description about two PCI devices]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-06-14 12:28:59 -04:00
..
hotplug PCI changes for the v3.10 merge window: 2013-04-29 09:30:25 -07:00
pcie PCI changes for the v3.10 merge window: 2013-04-29 09:30:25 -07:00
access.c PCI: Fix PCI Express Capability accessors for PCI_EXP_FLAGS 2013-02-15 11:46:24 -07:00
ats.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-01-11 18:50:26 -08:00
bus.c PCI: Delay final fixups until resources are assigned 2013-05-07 14:35:44 -06:00
host-bridge.c PCI: add host bridge release support 2012-04-30 14:52:43 -06:00
hotplug-pci.c PCI: hotplug: remove pci_do_scan_bus() 2012-06-13 15:42:27 -06:00
htirq.c pci: Fix files needing export.h for EXPORT_SYMBOL/THIS_MODULE 2011-10-31 19:31:22 -04:00
ioapic.c PCI changes for the v3.8 merge window: 2012-12-13 12:14:47 -08:00
iov.c pci: Add SRIOV helper function to determine if VFs are assigned to guest 2013-04-24 19:31:58 -07:00
irq.c PCI: Convert dev_printk(KERN_<LEVEL> to dev_<level>( 2012-11-07 15:24:18 -07:00
Kconfig PCI: Drop bogus default from ARCH_SUPPORTS_MSI 2012-09-10 16:49:52 -06:00
Makefile PCI: Always build setup-bus when PCI is enabled 2012-11-28 13:00:58 -08:00
msi.c PCI: Set ->mask_pos correctly 2013-04-30 08:49:19 -07:00
of.c PCI: OF: Don't crash when bridge parent is NULL. 2011-08-19 08:51:37 -07:00
pci-acpi.c PCI changes for the v3.10 merge window: 2013-04-29 09:30:25 -07:00
pci-driver.c PCI: Don't try to disable Bus Master on disconnected PCI devices 2013-04-02 18:03:09 -06:00
pci-label.c switch ->is_visible() to returning umode_t 2012-01-03 22:54:55 -05:00
pci-stub.c PCI: Convert dev_printk(KERN_<LEVEL> to dev_<level>( 2012-11-07 15:24:18 -07:00
pci-sysfs.c PCI: Use vma_pages() to replace (vm_end - vm_start) >> PAGE_SHIFT 2013-04-15 14:30:44 -06:00
pci.c Merge branch 'pci/rafael-pm' into next 2013-04-17 10:43:16 -06:00
pci.h PCI: Remove "extern" from function declarations 2013-04-17 10:21:17 -06:00
probe.c PCI updates for v3.10: 2013-05-09 10:21:44 -07:00
proc.c proc: Supply a function to remove a proc entry by PDE 2013-05-01 17:29:46 -04:00
quirks.c PCI: Clean up quirk_io_region 2013-04-15 14:30:44 -06:00
remove.c PCI: Add pcibios hooks for adding and removing PCI buses 2013-04-12 15:38:25 -06:00
rom.c PCI: Add PCI ROM helper for platform-provided ROM images 2013-03-26 17:19:41 -06:00
search.c PCI: Fix reference count leak in pci_dev_present() 2013-01-25 13:49:27 -07:00
setup-bus.c PCI: Warn about failures instead of "must_check" functions 2013-04-17 10:21:12 -06:00
setup-irq.c PCI: Provide a default pcibios_update_irq() 2012-09-18 17:28:21 -06:00
setup-res.c PCI: Remove unused variables 2013-04-15 10:56:27 -06:00
slot.c PCI: Warn about failures instead of "must_check" functions 2013-04-17 10:21:12 -06:00
syscall.c
vpd.c pci: Fix files needing export.h for EXPORT_SYMBOL/THIS_MODULE 2011-10-31 19:31:22 -04:00
xen-pcifront.c xen/pcifront: Deal with toolstack missing 'XenbusStateClosing' state. 2013-06-14 12:28:59 -04:00