This series is against the latest tip tree.

Currently multiple MSI mode is limited to a single vector per device (at
least on x86 and PPC). This series breathes life into pci_enable_msi_block()
and makes it possible to set interrupt affinity for multiple IRQs, similarly
to MSI-X. Yet, only for x86 and only when IOMMUs are present.

Although IRQ and PCI subsystems are modified, the current behaviour left
intact. The drivers could just start using multiple MSIs just by following
the existing documentation.

The AHCI device driver makes use of the new mode and a new function -
pci_enable_msi_block_auto() - patches 4,5.

Changes since v1:
  4/5:	based on Bjorn's review pci_enable_msi_block_auto() returns
	the number of interrupts allocated or error code

  5/5:	based on Jeff's comments:

	- AHCI specific code moved from libata-core.c to libahci.c;

	- the host-wide lock concern addressed - ahci_interrupt() handler
	  split in two parts: ahci_hw_interrupt() hardware context handler
	  and ahci_thread_fn() threaded handler;

	- host->lock statistics attached;

Host-wide lock statistics summary:

  Taken using command 'if=/dev/sd{a,b,c} of=/dev/null' running in parallel
  on three SATA HDDs:
	ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
	ata2: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
	ata3: SATA link up 3.0 Gbps (SStatus 123 SControl 300)

  ahci_interrupt()
  Capabilities: [80] MSI: Enable+ Count=1/16 Maskable- 64bit-

Test	holdtime-total	waittime-total	acquis.	holdtime-avg	waittime-avg
#
01.	22565801.27	93056.41	6377094	3.538571216	0.014592291
02.	20358324.12	60825.47	6411012	3.175524257	0.009487655
03.	21190730.38	63610.38	6384508	3.319085884	0.009963239
04.	22491064.54	80624.96	6398390	3.515113105	0.012600820
05.	21986193.10	78034.38	6379092	3.446602291	0.012232835
06.	20556437.70	62314.64	6287673	3.269323596	0.009910604
07.	20477137.55	66190.92	6388507	3.205308776	0.010360937
08.	21442240.03	69306.80	6402109	3.349246323	0.010825620
						-----------	-----------
avg						3.352346931	0.011246750

  ahci_hw_interrupt()
  Capabilities: [80] MSI: Enable+ Count=16/16 Maskable- 64bit-

Test	holdtime-total	waittime-total	acquis.	holdtime-avg	waittime-avg
#
09.	8936643.32	54559.79	6505606	1.373683454	0.008386581
10.	8579972.36	51496.56	6496233	1.320761180	0.007927142
11.	8138708.47	54061.46	6494647	1.253141005	0.008324003
12.	8322068.81	60427.51	6509975	1.278356493	0.009282295
13.	8527745.18	65978.83	6515589	1.308821839	0.010126303
14.	8662461.99	57291.39	6510702	1.330495850	0.008799572
15.	8054911.26	69186.41	6514262	1.236504037	0.010620759
16.	9618631.17	39726.37	6517385	1.475842101	0.006095446
						-----------	-----------
avg						1.322200745	0.008695263
Attached patches:
  1/5: x86, MSI: Support multiple MSIs in presense of IRQ remapping
  2/5: x86, MSI: Allocate as many multiple IRQs as requested
  3/5: x86, MSI: Minor readability fixes
  4/5: PCI, MSI: Enable multiple MSIs with pci_enable_msi_block_auto()
  5/5: AHCI: Support multiple MSIs

 Documentation/PCI/MSI-HOWTO.txt |   37 ++++++-
 arch/x86/kernel/apic/io_apic.c  |  170 +++++++++++++++++++++++++++++--
 drivers/ata/ahci.c              |   14 ++-
 drivers/ata/ahci.h              |    5 +
 drivers/ata/libahci.c           |  211 +++++++++++++++++++++++++++++++++++++-
 drivers/pci/msi.c               |   36 ++++++-
 include/linux/irq.h             |    6 +
 include/linux/msi.h             |    1 +
 include/linux/pci.h             |    7 ++
 kernel/irq/chip.c               |   30 ++++--
 kernel/irq/irqdesc.c            |   31 ++++++
 11 files changed, 509 insertions(+), 39 deletions(-)

-- 
1.7.7.6


-- 
Regards,
Alexander Gordeev
agordeev@redhat.com