[patch V2 00/31] genirq/msi, PCI/MSI: Spring cleaning - Part 3

Thomas Gleixner
2021-12-06T22:51:23Z

This is the third part of [PCI]MSI refactoring which aims to provide the
ability of expanding MSI-X vectors after enabling MSI-X.

The first two parts of this work can be found here:

https://lore.kernel.org/r/20211206210147.872865823@linutronix.de
https://lore.kernel.org/r/20211206210307.625116253@linutronix.de

This third part has the following important changes:

1) Add locking to protect the MSI descriptor storage

Right now the MSI descriptor storage (linked list) is not protected
by anything under the assumption that the list is installed before
use and destroyed after use. As this is about to change there has to
be protection

2) A new set of iterators which allow filtering on the state of the
descriptors namely whether a descriptor is associated to a Linux
interrupt or not.

This cleans up a lot of use cases which have to do this filtering
manually.

3) A new set of MSI descriptor allocation functions which make the usage
sites simpler and confine the storage handling to the core code.

Trivial MSI descriptors (non PCI) are now allocated by the core code
automatically when the underlying irq domain requests that.

4) Rework of sysfs handling to prepare for dynamic extension of MSI-X

The current mechanism which creates the directory and the attributes
for all MSI descriptors in one go is obviously not suitable for
dynamic extension. The rework splits the directory creation out and
lets the MSI interrupt allocation create the per descriptor
attributes.

5) Conversion of the MSI descriptor storage to xarray

The linked list based storage is suboptimal even without dynamic
expansion as it requires full list walks to get to a specific
descriptor. With dynamic expansion this gets even more
convoluted. Xarray is way more suitable and simplifies the
final goal of dynamic expansion of the MSI-X space.

This third series is based on:

git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git msi-v2-part-2

and also available from git:

git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git msi-v2-part-3

V1 of this series can be found here:

https://lore.kernel.org/r/20211126224100.303046749@linutronix.de

Changes versus V1:

- Remove the allocation counter patch as it is not required

- Fix the powerpc fallout - Cedric

- Fix the CONFIG typo - Niklas

- Picked up Reviewed/Tested/Acked-by tags as appropriate

As a consequence of the discussion vs. the general direction of these
patches, part 4 is not going to be updated in it's current form.

The assumption that MSI[X] and IMS are mutually exclusive and that IMS is
basically an extension for finer grained splitup of the PCI device does not
hold.

There is a plan to refactor the code further in order to provide the
desired functionality of MSI[X]/IMS which will also gain the dynamic
extension of MSI-X vectors:

https://lore.kernel.org/r/87o85v3znb.ffs@tglx

Thanks,

tglx
---
.clang-format | 1
arch/powerpc/platforms/4xx/hsta_msi.c | 7
arch/powerpc/platforms/cell/axon_msi.c | 7
arch/powerpc/platforms/pasemi/msi.c | 9
arch/powerpc/sysdev/fsl_msi.c | 8
arch/powerpc/sysdev/mpic_u3msi.c | 9
arch/s390/pci/pci_irq.c | 6
arch/x86/pci/xen.c | 14
drivers/base/core.c | 3
drivers/base/platform-msi.c | 110 -----
drivers/bus/fsl-mc/fsl-mc-msi.c | 61 --
drivers/ntb/msi.c | 19
drivers/pci/controller/pci-hyperv.c | 15
drivers/pci/msi/irqdomain.c | 11
drivers/pci/msi/legacy.c | 20
drivers/pci/msi/msi.c | 258 ++++++------
drivers/pci/xen-pcifront.c | 2
drivers/soc/ti/ti_sci_inta_msi.c | 77 +--
include/linux/device.h | 4
include/linux/msi.h | 107 +++--
include/linux/soc/ti/ti_sci_inta_msi.h | 1
kernel/irq/msi.c | 700 ++++++++++++++++++++++-----------
22 files changed, 794 insertions(+), 655 deletions(-)