linux-kernel - Re: [PATCH 1/2] PCI: Setup bridge resources earlier

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Message-ID: <b587595c-98f5-dd5a-31a2-6265bff1dc3a@linux.intel.com>
Date: Tue, 14 Oct 2025 14:20:11 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Guenter Roeck <linux@...ck-us.net>
cc: linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>, 
    Krzysztof Wilczyński <kw@...ux.com>, 
    "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, 
    LKML <linux-kernel@...r.kernel.org>, 
    Lucas De Marchi <lucas.demarchi@...el.com>
Subject: Re: [PATCH 1/2] PCI: Setup bridge resources earlier

On Mon, 13 Oct 2025, Guenter Roeck wrote:
> On Wed, Sep 24, 2025 at 04:42:27PM +0300, Ilpo Järvinen wrote:
> > Bridge windows are read twice from PCI Config Space, the first read is
> > made from pci_read_bridge_windows() which does not setup the device's
> > resources. It causes problems down the road as child resources of the
> > bridge cannot check whether they reside within the bridge window or
> > not.
> > 
> > Setup the bridge windows already in pci_read_bridge_windows().
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > ---
> 
> This patch causes some boot test failures for me. Specifically, booting
> alpha images from PCI through a PCI bridge fails. Reverting it fixes
> the problem.
> 
> Bisect log attached for reference.
> 
> Guenter
> 
> ---
> # bad: [3a8660878839faadb4f1a6dd72c3179c1df56787] Linux 6.18-rc1
> # good: [e5f0a698b34ed76002dc5cff3804a61c80233a7a] Linux 6.17
> git bisect start 'HEAD' 'v6.17'
> # good: [58809f614e0e3f4e12b489bddf680bfeb31c0a20] Merge tag 'drm-next-2025-10-01' of https://gitlab.freedesktop.org/drm/kernel
> git bisect good 58809f614e0e3f4e12b489bddf680bfeb31c0a20
> # good: [bed0653fe2aacb0ca8196075cffc9e7062e74927] Merge tag 'iommu-updates-v6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/iommu/linux
> git bisect good bed0653fe2aacb0ca8196075cffc9e7062e74927
> # good: [6a74422b9710e987c7d6b85a1ade7330b1e61626] Merge tag 'mips_6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux
> git bisect good 6a74422b9710e987c7d6b85a1ade7330b1e61626
> # bad: [522ba450b56fff29f868b1552bdc2965f55de7ed] Merge tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux
> git bisect bad 522ba450b56fff29f868b1552bdc2965f55de7ed
> # bad: [256e3417065b2721f77bcd37331796b59483ef3b] Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
> git bisect bad 256e3417065b2721f77bcd37331796b59483ef3b
> # bad: [2f2c7254931f41b5736e3ba12aaa9ac1bbeeeb92] Merge tag 'pci-v6.18-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci
> git bisect bad 2f2c7254931f41b5736e3ba12aaa9ac1bbeeeb92
> # bad: [531abff0fa53bc3a2f7f69b2693386eb6bda96e5] Merge branch 'pci/controller/qcom'
> git bisect bad 531abff0fa53bc3a2f7f69b2693386eb6bda96e5
> # bad: [fead6a0b15bf3b33dba877efec6b4e7b4cc4abc3] Merge branch 'pci/resource'
> git bisect bad fead6a0b15bf3b33dba877efec6b4e7b4cc4abc3
> # good: [0bb65e32495e6235a069b60e787140da99e9c122] Merge branch 'pci/p2pdma'
> git bisect good 0bb65e32495e6235a069b60e787140da99e9c122
> # good: [ebe091ad81e1d3e5cbb1592ebc18175b5ca3d2bd] PCI: Use pbus_select_window_for_type() during IO window sizing
> git bisect good ebe091ad81e1d3e5cbb1592ebc18175b5ca3d2bd
> # good: [15c5867b0ae6a47914b45daf3b64e2d2aceb4ee5] PCI: Don't print stale information about resource
> git bisect good 15c5867b0ae6a47914b45daf3b64e2d2aceb4ee5
> # good: [dc32e9346b26ba33e84ec3034a1e53a9733700f9] PCI/pwrctrl: Fix device leak at device stop
> git bisect good dc32e9346b26ba33e84ec3034a1e53a9733700f9
> # good: [4c5cd8d64172de3730056366dc61392a3f2f003a] Merge branch 'pci/pm'
> git bisect good 4c5cd8d64172de3730056366dc61392a3f2f003a
> # bad: [a43ac325c7cbbfe72bdf9178059b3ee9f5a2c7dd] PCI: Set up bridge resources earlier
> git bisect bad a43ac325c7cbbfe72bdf9178059b3ee9f5a2c7dd
> # first bad commit: [a43ac325c7cbbfe72bdf9178059b3ee9f5a2c7dd] PCI: Set up bridge resources earlier

Hi,

Is it possible to get some logs from this (both good and bad would be 
the best so comparing is possible)?

I'm going to send a revert for the commit a43ac325c7cb ("PCI: Set up 
bridge resources earlier") today anyway because of another issue it caused
but as I'm planning to pursue the same change later, it would be useful to 
understand what goes wrong here so I know what additional supporting work 
is needed before coming back with this change.

-- 
 i.