linux-kernel - Re: [patch V2 34/46] PCI/MSI: Make arch_.*_msi

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Message-ID: <your-ad-here.call-01601123933-ext-6476@work.hours>
Date:   Sat, 26 Sep 2020 14:38:53 +0200
From:   Vasily Gorbik <gor@...ux.ibm.com>
To:     Thomas Gleixner <tglx@...utronix.de>, Qian Cai <cai@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        linux-s390@...r.kernel.org,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        linux-next@...r.kernel.org, x86@...nel.org,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, linux-hyperv@...r.kernel.org,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Jon Derrick <jonathan.derrick@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Wei Liu <wei.liu@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Steve Wahl <steve.wahl@....com>,
        Dimitri Sivanich <sivanich@....com>,
        Russ Anderson <rja@....com>, linux-pci@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        xen-devel@...ts.xenproject.org, Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Megha Dey <megha.dey@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jacob Pan <jacob.jun.pan@...el.com>,
        Baolu Lu <baolu.lu@...el.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [patch V2 34/46] PCI/MSI: Make arch_.*_msi_irq[s] fallbacks
 selectable

On Fri, Sep 25, 2020 at 09:54:52AM -0400, Qian Cai wrote:
> On Wed, 2020-08-26 at 13:17 +0200, Thomas Gleixner wrote:
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > The arch_.*_msi_irq[s] fallbacks are compiled in whether an architecture
> > requires them or not. Architectures which are fully utilizing hierarchical
> > irq domains should never call into that code.
> > 
> > It's not only architectures which depend on that by implementing one or
> > more of the weak functions, there is also a bunch of drivers which relies
> > on the weak functions which invoke msi_controller::setup_irq[s] and
> > msi_controller::teardown_irq.
> > 
> > Make the architectures and drivers which rely on them select them in Kconfig
> > and if not selected replace them by stub functions which emit a warning and
> > fail the PCI/MSI interrupt allocation.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> 
> Today's linux-next will have some warnings on s390x:
> 
> .config: https://gitlab.com/cailca/linux-mm/-/blob/master/s390.config
> 
> WARNING: unmet direct dependencies detected for PCI_MSI_ARCH_FALLBACKS
>   Depends on [n]: PCI [=n]
>   Selected by [y]:
>   - S390 [=y]
> 
> WARNING: unmet direct dependencies detected for PCI_MSI_ARCH_FALLBACKS
>   Depends on [n]: PCI [=n]
>   Selected by [y]:
>   - S390 [=y]
>

Yes, as well as on mips and sparc which also don't FORCE_PCI.
This seems to work for s390:

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index b0b7acf07eb8..41136fbe909b 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -192,3 +192,3 @@ config S390
        select PCI_MSI                  if PCI
-       select PCI_MSI_ARCH_FALLBACKS
+       select PCI_MSI_ARCH_FALLBACKS   if PCI
        select SET_FS