PCI access on removed devices

We observe that software's removing of a device generates potentially 1000's of MMIO and config space access when unbinding from the removed hardware, and this reliance on hardware to handle this slows down software's total tear down time for handling a removed device.

This series reduces the number of non-functional MMIO and config space accesses on a hot removed device. In some cases, we measure device unbinding that used to take 100's of milliseconds to complete in < 1ms.

v3 -> v4:

Merged up to current pci/hotplug.

The aer initialization is done only when CONFIG_PCIAER is enabled, similar to how ATS support is managed.

Removed making "is_removed" sticky on the checking pci_device_is_present. Only pciehp and pcie-dpc set this state in this series.

Added the MIPs dependency. This was okay'ed, but I don't see it in the linux-mips tree.

Keith Busch (5):
mips/pci: Reduce stack frame usage
pci: Add is_removed state
pci: No config access for removed devices
pcie/aer: Cache capability position
pci/msix: Skip disabling removed devices

 arch/mips/txx9/generic/pci.c       |  6 +-----
 drivers/pci/hotplug/pciehp_pci.c   |  2 ++
 drivers/pci/msi.c                  |  7 ++++++-
 drivers/pci/pcie/aer/aerdrv.c      | 10 +++++-----
 drivers/pci/pcie/aer/aerdrv_core.c | 12 ++++++------
 drivers/pci/pcie/pcie-dpc.c        |  1 +
 drivers/pci/probe.c                |  2 ++
 include/linux/pci.h                | 20 ++++++++++++++++++++
 8 files changed, 43 insertions(+), 17 deletions(-)

2.7.2