linux-kernel - Re: [PATCH 0/3] PCI & resource: Make coalescing host bridge windows safer

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Message-ID: <CAMuHMdUbseFEY8AGOxm2T8W-64qT9OSvfmvu+hyTJUT+WE2cVw@mail.gmail.com>
Date: Tue, 21 Oct 2025 09:44:31 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Kai-Heng Feng <kaihengf@...dia.com>, Rob Herring <robh@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Krzysztof Wilczyński <kw@...ux.com>, 
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH 0/3] PCI & resource: Make coalescing host bridge windows safer

Hi Ilpo,

On Mon, 20 Oct 2025 at 18:20, Ilpo Järvinen
<ilpo.jarvinen@...ux.intel.com> wrote:
> On Mon, 20 Oct 2025, Geert Uytterhoeven wrote:
> > On Fri, 10 Oct 2025 at 16:42, Ilpo Järvinen
> > <ilpo.jarvinen@...ux.intel.com> wrote:
> > > Here's a series for Geert to test if this fixes the improper coalescing
> > > of resources as was experienced with the pci_add_resource() change (I
> > > know the breaking change was pulled before 6.18 main PR but I'd want to
> > > retry it later once the known issues have been addressed). The expected
> > > result is there'll be two adjacent host bridge resources in the
> > > resource tree as the different name should disallow coalescing them
> > > together, and therefore BAR0 has a window into which it belongs to.
> > >
> > > Generic info for the series:
> > >
> > > PCI host bridge windows were coalesced in place into one of the structs
> > > on the resources list. The host bridge window coalescing code does not
> > > know who holds references and still needs the struct resource it's
> > > coalescing from/to so it is safer to perform coalescing into entirely
> > > a new struct resource instead and leave the old resource addresses as
> > > they were.
> > >
> > > The checks when coalescing is allowed are also made stricter so that
> > > only resources that have identical the metadata can be coalesced.
> > >
> > > As a bonus, there's also a bit of framework to easily create kunit
> > > tests for resource tree functions (beyond just resource_coalesce()).
> > >
> > > Ilpo Järvinen (3):
> > >   PCI: Refactor host bridge window coalescing loop to use prev
> > >   PCI: Do not coalesce host bridge resource structs in place
> > >   resource, kunit: add test case for resource_coalesce()
> >
> > Thanks for your series!
> >
> > I have applied this on top of commit 06b77d5647a4d6a7 ("PCI:
> > Mark resources IORESOURCE_UNSET when outside bridge windows"), and
> > gave it a a try on Koelsch (R-Car M2-W).
>
> So the pci_bus_add_resource() patch to rcar_pci_probe() was not included?
> No coalescing would be attempted without that change.

Sorry, I didn't realize you wanted that (and anything else) to be
included, too.  Please tell me the exact base I should use for testing,
and I will give it another run.
Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds