Re: [patch 00/22] genirq/msi, PCI/MSI: Spring cleaning - Part 1

Cédric Le Goater
2021-11-29T14:54:23Z

On 11/27/21 02:18, Thomas Gleixner wrote:
> The [PCI] MSI code has gained quite some warts over time. A recent
> discussion unearthed a shortcoming: the lack of support for expanding
> PCI/MSI-X vectors after initialization of MSI-X.
>
> PCI/MSI-X has no requirement to setup all vectors when MSI-X is enabled in
> the device. The non-used vectors have just to be masked in the vector
> table. For PCI/MSI this is not possible because the number of vectors
> cannot be changed after initialization.
>
> The PCI/MSI code, but also the core MSI irq domain code are built around
> the assumption that all required vectors are installed at initialization
> time and freed when the device is shut down by the driver.
>
> Supporting dynamic expansion at least for MSI-X is important for VFIO so
> that the host side interrupts for passthrough devices can be installed on
> demand.
>
> This is the first part of a large (total 101 patches) series which
> refactors the [PCI]MSI infrastructure to make runtime expansion of MSI-X
> vectors possible. The last part (10 patches) provide this functionality.
>
> The first part is mostly a cleanup which consolidates code, moves the PCI
> MSI code into a separate directory and splits it up into several parts.
>
> No functional change intended except for patch 2/N which changes the
> behaviour of pci_get_vector()/affinity() to get rid of the assumption that
> the provided index is the "index" into the descriptor list instead of using
> it as the actual MSI[X] index as seen by the hardware. This would break
> users of sparse allocated MSI-X entries, but non of them use these
> functions.
>
> This series is based on 5.16-rc2 and also available via git:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git msi-v1-part-1
>
> For the curious who can't wait for the next part to arrive the full series
> is available via:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git msi-v1-part-4

After fixing the compile failures, I didn't see any regressions on
these platforms :

PowerNV, pSeries under KVM and PowerVM, using POWER8/9 processors.

Thanks,

C.

> Thanks,
>
> tglx
> ---
> arch/powerpc/platforms/4xx/msi.c | 281 ------------
> b/Documentation/driver-api/pci/pci.rst | 2
> b/arch/mips/pci/msi-octeon.c | 32 -
> b/arch/powerpc/platforms/4xx/Makefile | 1
> b/arch/powerpc/platforms/cell/axon_msi.c | 2
> b/arch/powerpc/platforms/powernv/pci-ioda.c | 4
> b/arch/powerpc/platforms/pseries/msi.c | 6
> b/arch/powerpc/sysdev/Kconfig | 6
> b/arch/s390/pci/pci_irq.c | 4
> b/arch/sparc/kernel/pci_msi.c | 4
> b/arch/x86/hyperv/irqdomain.c | 55 --
> b/arch/x86/include/asm/x86_init.h | 6
> b/arch/x86/include/asm/xen/hypervisor.h | 8
> b/arch/x86/kernel/apic/msi.c | 8
> b/arch/x86/kernel/x86_init.c | 12
> b/arch/x86/pci/xen.c | 19
> b/drivers/irqchip/irq-gic-v2m.c | 1
> b/drivers/irqchip/irq-gic-v3-its-pci-msi.c | 1
> b/drivers/irqchip/irq-gic-v3-mbi.c | 1
> b/drivers/net/wireless/ath/ath11k/pci.c | 2
> b/drivers/pci/Makefile | 3
> b/drivers/pci/msi/Makefile | 7
> b/drivers/pci/msi/irqdomain.c | 267 +++++++++++
> b/drivers/pci/msi/legacy.c | 79 +++
> b/drivers/pci/msi/msi.c | 645 ++++------------------------
> b/drivers/pci/msi/msi.h | 39 +
> b/drivers/pci/msi/pcidev_msi.c | 43 +
> b/drivers/pci/pci-sysfs.c | 7
> b/drivers/pci/xen-pcifront.c | 2
> b/include/linux/msi.h | 135 ++---
> b/include/linux/pci.h | 1
> b/kernel/irq/msi.c | 41 +
> 32 files changed, 696 insertions(+), 1028 deletions(-)
>