linux-kernel - Re: [PATCH v2] PCI: Coalesce contiguous regions for host bridges

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Message-ID: <CAAd53p7s=k7pa_GdaetQGQYp9GbQR+jkQWLQoe6-c0oTjCQXxw@mail.gmail.com>
Date:   Mon, 12 Jul 2021 11:50:45 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] PCI: Coalesce contiguous regions for host bridges

Hi Guenter,

On Sat, Jul 10, 2021 at 7:15 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> Hi,
>
> On Thu, Apr 01, 2021 at 09:12:52PM +0800, Kai-Heng Feng wrote:
> > Built-in graphics on HP EliteDesk 805 G6 doesn't work because graphics
> > can't get the BAR it needs:
> > [    0.611504] pci_bus 0000:00: root bus resource [mem 0x10020200000-0x100303fffff window]
> > [    0.611505] pci_bus 0000:00: root bus resource [mem 0x10030400000-0x100401fffff window]
> > ...
> > [    0.638083] pci 0000:00:08.1:   bridge window [mem 0xd2000000-0xd23fffff]
> > [    0.638086] pci 0000:00:08.1:   bridge window [mem 0x10030000000-0x100401fffff 64bit pref]
> > [    0.962086] pci 0000:00:08.1: can't claim BAR 15 [mem 0x10030000000-0x100401fffff 64bit pref]: no compatible bridge window
> > [    0.962086] pci 0000:00:08.1: [mem 0x10030000000-0x100401fffff 64bit pref] clipped to [mem 0x10030000000-0x100303fffff 64bit pref]
> > [    0.962086] pci 0000:00:08.1:   bridge window [mem 0x10030000000-0x100303fffff 64bit pref]
> > [    0.962086] pci 0000:07:00.0: can't claim BAR 0 [mem 0x10030000000-0x1003fffffff 64bit pref]: no compatible bridge window
> > [    0.962086] pci 0000:07:00.0: can't claim BAR 2 [mem 0x10040000000-0x100401fffff 64bit pref]: no compatible bridge window
> >
> > However, the root bus has two contiguous regions that can contain the
> > child resource requested.
> >
> > Bjorn Helgaas pointed out that we can simply coalesce contiguous regions
> > for host bridges, since host bridge don't have _SRS. So do that
> > accordingly to make child resource can be contained. This change makes
> > the graphics works on the system in question.
> >
> > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212013
> > Suggested-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>
> With this patch in place, I can no longer boot the ppc:sam460ex
> qemu emulation from nvme. I see the following boot error:
>
> nvme nvme0: Device not ready; aborting initialisation, CSTS=0x0
> nvme nvme0: Removing after probe failure status: -19
>
> A key difference seems to be swapped region addresses:
>
> ok:
>
> PCI host bridge to bus 0002:00^M
> pci_bus 0002:00: root bus resource [io  0x0000-0xffff]
> pci_bus 0002:00: root bus resource [mem 0xd80000000-0xdffffffff] (bus address [0x80000000-0xffffffff])
> pci_bus 0002:00: root bus resource [mem 0xc0ee00000-0xc0eefffff] (bus address [0x00000000-0x000fffff])
>
> bad:
>
> PCI host bridge to bus 0002:00^M
> pci_bus 0002:00: root bus resource [io  0x0000-0xffff]
> pci_bus 0002:00: root bus resource [mem 0xc0ee00000-0xc0eefffff] (bus address [0x00000000-0x000fffff])
> pci_bus 0002:00: root bus resource [mem 0xd80000000-0xdffffffff] (bus address [0x80000000-0xffffffff])
>
> and then bar address assignments are swapped/changed.
>
> ok:
>
> pci 0002:00:06.0: BAR 0: assigned [mem 0xd80000000-0xd83ffffff]^M
> pci 0002:00:06.0: BAR 1: assigned [mem 0xd84000000-0xd841fffff]^M
> pci 0002:00:02.0: BAR 0: assigned [mem 0xd84200000-0xd84203fff 64bit]^M
> pci 0002:00:01.0: BAR 5: assigned [mem 0xd84204000-0xd842041ff]^M
> pci 0002:00:03.0: BAR 0: assigned [io  0x1000-0x107f]^M
> pci 0002:00:03.0: BAR 1: assigned [mem 0xd84204200-0xd8420427f]^M
> pci 0002:00:01.0: BAR 4: assigned [io  0x1080-0x108f]^M
> pci 0002:00:01.0: BAR 0: assigned [io  0x1090-0x1097]^M
> pci 0002:00:01.0: BAR 2: assigned [io  0x1098-0x109f]^M
> pci 0002:00:01.0: BAR 1: assigned [io  0x10a0-0x10a3]^M
> pci 0002:00:01.0: BAR 3: assigned [io  0x10a4-0x10a7]^M
> pci_bus 0002:00: resource 4 [io  0x0000-0xffff]^M
> pci_bus 0002:00: resource 5 [mem 0xd80000000-0xdffffffff]^M
> pci_bus 0002:00: resource 6 [mem 0xc0ee00000-0xc0eefffff]^M
>
> bad:
>
> pci 0002:00:06.0: BAR 0: assigned [mem 0xd80000000-0xd83ffffff]^M
> pci 0002:00:06.0: BAR 1: assigned [mem 0xd84000000-0xd841fffff]^M
> pci 0002:00:02.0: BAR 0: assigned [mem 0xc0ee00000-0xc0ee03fff 64bit]^M
> pci 0002:00:01.0: BAR 5: assigned [mem 0xc0ee04000-0xc0ee041ff]^M
> pci 0002:00:03.0: BAR 0: assigned [io  0x1000-0x107f]^M
> pci 0002:00:03.0: BAR 1: assigned [mem 0xc0ee04200-0xc0ee0427f]^M
> pci 0002:00:01.0: BAR 4: assigned [io  0x1080-0x108f]^M
> pci 0002:00:01.0: BAR 0: assigned [io  0x1090-0x1097]^M
> pci 0002:00:01.0: BAR 2: assigned [io  0x1098-0x109f]^M
> pci 0002:00:01.0: BAR 1: assigned [io  0x10a0-0x10a3]^M
> pci 0002:00:01.0: BAR 3: assigned [io  0x10a4-0x10a7]^M
> pci_bus 0002:00: resource 4 [io  0x0000-0xffff]^M
> pci_bus 0002:00: resource 5 [mem 0xc0ee00000-0xc0eefffff]^M
> pci_bus 0002:00: resource 6 [mem 0xd80000000-0xdffffffff]^M
>
> Reverting this patch fixes the problem.

Can you please comment out the list_sort()? Seems like the precaution
breaks your system...

Kai-Heng

>
> Guenter
>
> ---
> bisect log:
>
> # bad: [f55966571d5eb2876a11e48e798b4592fa1ffbb7] Merge tag 'drm-next-2021-07-08-1' of git://anongit.freedesktop.org/drm/drm
> # good: [e9f1cbc0c4114880090c7a578117d3b9cf184ad4] Merge tag 'acpi-5.14-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
> git bisect start 'f55966571d5e' 'e9f1cbc0c411'
> # bad: [b0dfd9af28b60d7ec42c359ae84c1ba97e093100] Merge tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux
> git bisect bad b0dfd9af28b60d7ec42c359ae84c1ba97e093100
> # bad: [364a716bd73e9846d3118a43f600f8f517658b38] Merge branch 'pci/host/intel-gw'
> git bisect bad 364a716bd73e9846d3118a43f600f8f517658b38
> # good: [c9fb9042c98df94197a1ba4cf14a77c8053b0fae] Merge branch 'pci/p2pdma'
> git bisect good c9fb9042c98df94197a1ba4cf14a77c8053b0fae
> # bad: [7132700067f234d37c234e5d711bb49ea06d2352] Merge branch 'pci/sysfs'
> git bisect bad 7132700067f234d37c234e5d711bb49ea06d2352
> # bad: [131e4f76c9ae9636046bf04d19d43af0e4ae9807] Merge branch 'pci/resource'
> git bisect bad 131e4f76c9ae9636046bf04d19d43af0e4ae9807
> # good: [411e2a43d210e98730713acf6d01dcf823ee35e3] PCI: Work around Huawei Intelligent NIC VF FLR erratum
> git bisect good 411e2a43d210e98730713acf6d01dcf823ee35e3
> # good: [e92605b0a0cdafb6c37b9d1ad24fe1cf8280eeb6] Merge branch 'pci/pm'
> git bisect good e92605b0a0cdafb6c37b9d1ad24fe1cf8280eeb6
> # bad: [65db04053efea3f3e412a7e0cc599962999c96b4] PCI: Coalesce host bridge contiguous apertures
> git bisect bad 65db04053efea3f3e412a7e0cc599962999c96b4
> # first bad commit: [65db04053efea3f3e412a7e0cc599962999c96b4] PCI: Coalesce host bridge contiguous apertures