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

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Message-ID: <ee815cd9-03f3-02f2-a269-ad79ca2af742@kaod.org>
Date:   Mon, 29 Nov 2021 10:52:26 +0100
From:   Cédric Le Goater <clg@...d.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
CC:     <linux-hyperv@...r.kernel.org>, Paul Mackerras <paulus@...ba.org>,
        <sparclinux@...r.kernel.org>, Wei Liu <wei.liu@...nel.org>,
        Ashok Raj <ashok.raj@...el.com>, Marc Zygnier <maz@...nel.org>,
        <x86@...nel.org>, Christian Borntraeger <borntraeger@...ibm.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Jason Gunthorpe <jgg@...dia.com>, <linux-pci@...r.kernel.org>,
        <xen-devel@...ts.xenproject.org>, <ath11k@...ts.infradead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Megha Dey <megha.dey@...el.com>,
        Juergen Gross <jgross@...e.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-mips@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [patch 00/22] genirq/msi, PCI/MSI: Spring cleaning - Part 1

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(-)
>