[Qemu-devel] [PATCH v7 0/4] piix_pci: optimize irq data path

[Isaku Yamahata <yamahata@valinux.co.jp>]

Here is v7 which are rebased to pci branch.

I tested this patch series as follows. please see the commit message
for details.
- 3/4 piix_pci: optimize set irq path
  Run linux as guest with 4 e1000 emulated devices.
  And confirmed that each PIRQ[A-D] are able to assert interrupts.
- 4/4 piix_pci: load path clean up
  Run linux as guest with one e1000 emulated device.
  savevm/loadvm guest with runing ping -f in guest.

To be honest, the patch, "4/4 piix_pci: load path clean up", needs more
extensive tests. For example live migration and stress test.
But for now I don't have plan to further testing in near future. Sorry.
So please feel free to pick or drop the last patch.

patch description:
This patch series optimizes irq data path of piix_pci.
So far piix3 tracks each pirq level and checks whether a given pic pins is
asserted by seeing if each pirq is mapped into the pic pin.
This is independent on irq routing, but data path is on slow path.

Given that irq routing is rarely changed and asserting pic pins is on
data path, the path that asserts pic pins should be optimized and
chainging irq routing should be on slow path.
The new behavior with this patch series is to use bitmap which is addressed
by pirq and pic pins with a given irq routing.
When pirq is asserted, the bitmap is set and see if the pic pins is
asserted by checking the bitmaps.
When irq routing is changed, rebuild the bitmap and re-assert pic pins.

Changes v6 -> v7:
- rebased to pci branch
- added how to test to the commit message

Changes v5 -> v6:
- fixed piix3_set_irq_pic()

Changes v4 -> v5:
- typo

Changes v3 -> v4:
- use pirq, pci_intx instead of irq_num in piix_pci.c
- use symbolic constant PIC_NUM_PINS
- introduced new patch 4/4 which cleans up a bit.

Changes v2 -> v3:
- s/dummy_for_save_load_compat/pci_irq_levels_vmstate/g
- move down unused member of pci_irq_levels_vmstate in the structure
  for cache efficiency

Changes v1 -> v2:
- addressed review comments.

Isaku Yamahata (4):
  pci: add accessor function to get irq levels
  piix_pci: eliminate PIIX3State::pci_irq_levels
  piix_pci: optimize set irq path
  piix_pci: load path clean up

 hw/pci.c      |    7 +++
 hw/pci.h      |    1 +
 hw/piix_pci.c |  129 ++++++++++++++++++++++++++++++++++++++++++++++-----------
 3 files changed, 112 insertions(+), 25 deletions(-)