Message-ID: <CAMuHMdU_tPmQd=9dCzNs+dEt3fHNsYpYPFnT6QZk546o-J-y9g@mail.gmail.com>
Date: Thu, 2 Oct 2025 17:25:39 +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>, 
	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>, 
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH 2/2] PCI: Resources outside their window must set IORESOURCE_UNSET

Hi Ilpo,

On Thu, 2 Oct 2025 at 16:54, Ilpo Järvinen
<ilpo.jarvinen@...ux.intel.com> wrote:
> On Wed, 1 Oct 2025, Geert Uytterhoeven wrote:
> > On Wed, 1 Oct 2025 at 15:06, Ilpo Järvinen
> > <ilpo.jarvinen@...ux.intel.com> wrote:
> > > On Wed, 1 Oct 2025, Geert Uytterhoeven wrote:
> > > > On Tue, 30 Sept 2025 at 18:32, Ilpo Järvinen
> > > > <ilpo.jarvinen@...ux.intel.com> wrote:
> > > > > On Tue, 30 Sep 2025, Geert Uytterhoeven wrote:
> > > > > > On Fri, 26 Sept 2025 at 04:40, Ilpo Järvinen
> > > > > > <ilpo.jarvinen@...ux.intel.com> wrote:
> > > > > > > PNP resources are checked for conflicts with the other resource in the
> > > > > > > system by quirk_system_pci_resources() that walks through all PCI
> > > > > > > resources. quirk_system_pci_resources() correctly filters out resource
> > > > > > > with IORESOURCE_UNSET.
> > > > > > >
> > > > > > > Resources that do not reside within their bridge window, however, are
> > > > > > > not properly initialized with IORESOURCE_UNSET resulting in bogus
> > > > > > > conflicts detected in quirk_system_pci_resources():
> > > > > > >
> > > > > > > pci 0000:00:02.0: VF BAR 2 [mem 0x00000000-0x1fffffff 64bit pref]
> > > > > > > pci 0000:00:02.0: VF BAR 2 [mem 0x00000000-0xdfffffff 64bit pref]: contains BAR 2 for 7 VFs
> > > > > > > ...
> > > > > > > pci 0000:03:00.0: VF BAR 2 [mem 0x00000000-0x1ffffffff 64bit pref]
> > > > > > > pci 0000:03:00.0: VF BAR 2 [mem 0x00000000-0x3dffffffff 64bit pref]: contains BAR 2 for 31 VFs
> > > > > > > ...
> > > > > > > pnp 00:04: disabling [mem 0xfc000000-0xfc00ffff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xc0000000-0xcfffffff] because it overlaps 0000:00:02.0 BAR 9 [mem 0x00000000-0xdfffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xfedc0000-0xfedc7fff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xfeda0000-0xfeda0fff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xfeda1000-0xfeda1fff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xc0000000-0xcfffffff disabled] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xfed20000-0xfed7ffff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xfed90000-0xfed93fff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xfed45000-0xfed8ffff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > > pnp 00:05: disabling [mem 0xfee00000-0xfeefffff] because it overlaps 0000:03:00.0 BAR 9 [mem 0x00000000-0x3dffffffff 64bit pref]
> > > > > > >
> > > > > > > Mark resources that are not contained within their bridge window with
> > > > > > > IORESOURCE_UNSET in __pci_read_base() which resolves the false
> > > > > > > positives for the overlap check in quirk_system_pci_resources().
> > > > > > >
> > > > > > > Fixes: f7834c092c42 ("PNP: Don't check for overlaps with unassigned PCI BARs")
> > > > > > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > > > > >
> > > > > > Thanks for your patch, which is now commit 06b77d5647a4d6a7 ("PCI:
> > > > > > Mark resources IORESOURCE_UNSET when outside bridge windows") in
> > > > > > linux-next/master next-20250929 pci/next
> > > >
> > > > > > This replaces the actual resources by their sizes in the boot log on
> > > > > > e.g. on R-Car M2-W:
> > > > > >
> > > > > >      pci-rcar-gen2 ee090000.pci: host bridge /soc/pci@...90000 ranges:
> > > > > >      pci-rcar-gen2 ee090000.pci:      MEM 0x00ee080000..0x00ee08ffff -> 0x00ee080000
> > > > > >      pci-rcar-gen2 ee090000.pci: PCI: revision 11
> > > > > >      pci-rcar-gen2 ee090000.pci: PCI host bridge to bus 0000:00
> > > > > >      pci_bus 0000:00: root bus resource [bus 00]
> > > > > >      pci_bus 0000:00: root bus resource [mem 0xee080000-0xee08ffff]
> > > > > >      pci 0000:00:00.0: [1033:0000] type 00 class 0x060000 conventional PCI endpoint
> > > > > >     -pci 0000:00:00.0: BAR 0 [mem 0xee090800-0xee090bff]
> > > > > >     -pci 0000:00:00.0: BAR 1 [mem 0x40000000-0x7fffffff pref]
> > > > >
> > > > > What is going to be the parent of these resources? They don't seem to fall
> > > > > under the root bus resource above in which case the output change is
> > > > > intentional so they don't appear as if address range would be "okay".
> > > >
> > > > >From /proc/iomem:
> > > >
> > > >     ee080000-ee08ffff : pci@...90000
> > > >       ee080000-ee080fff : 0000:00:01.0
> > > >         ee080000-ee080fff : ohci_hcd
> > > >       ee081000-ee0810ff : 0000:00:02.0
> > > >         ee081000-ee0810ff : ehci_hcd
> > > >     ee090000-ee090bff : ee090000.pci pci@...90000
> > >
> > > Okay, so this seem to appear in the resource tree but not among the root
> > > bus resources.
> > >
> > > >     ee0c0000-ee0cffff : pci@...d0000
> > > >       ee0c0000-ee0c0fff : 0001:01:01.0
> > > >         ee0c0000-ee0c0fff : ohci_hcd
> > > >       ee0c1000-ee0c10ff : 0001:01:02.0
> > > >         ee0c1000-ee0c10ff : ehci_hcd
> > > >
> > > > > When IORESOURCE_UNSET is set in a resource, %pR does not print the start
> > > > > and end addresses.
> > > >
> > > > Yeah, that's how I found this commit, without bisecting ;-)
> > > >
> > > > > >     +pci 0000:00:00.0: BAR 0 [mem size 0x00000400]
> > > > > >     +pci 0000:00:00.0: BAR 1 [mem size 0x40000000 pref]
> > > > > >      pci 0000:00:01.0: [1033:0035] type 00 class 0x0c0310 conventional PCI endpoint
> > > > > >     -pci 0000:00:01.0: BAR 0 [mem 0x00000000-0x00000fff]
> > > > > >     +pci 0000:00:01.0: BAR 0 [mem size 0x00001000]
> > > > >
> > > > > For this resource, it's very much intentional. It's a zero-based BAR which
> > > > > was left without IORESOURCE_UNSET prior to my patch leading to others part
> > > > > of the kernel to think that resource range valid and in use (in your
> > > > > case it's so small it wouldn't collide with anything but it wasn't
> > > > > properly set up resource, nonetheless).
> > > > >
> > > > > >      pci 0000:00:01.0: supports D1 D2
> > > > > >      pci 0000:00:01.0: PME# supported from D0 D1 D2 D3hot
> > > > > >      pci 0000:00:02.0: [1033:00e0] type 00 class 0x0c0320 conventional PCI endpoint
> > > > > >     -pci 0000:00:02.0: BAR 0 [mem 0x00000000-0x000000ff]
> > > > > >     +pci 0000:00:02.0: BAR 0 [mem size 0x00000100]
> > > > >
> > > > > And this as well is very much intentional.
> > > > >
> > > > > >      pci 0000:00:02.0: supports D1 D2
> > > > > >      pci 0000:00:02.0: PME# supported from D0 D1 D2 D3hot
> > > > > >      PCI: bus0: Fast back to back transfers disabled
> > > > > >      pci 0000:00:01.0: BAR 0 [mem 0xee080000-0xee080fff]: assigned
> > > > > >      pci 0000:00:02.0: BAR 0 [mem 0xee081000-0xee0810ff]: assigned
> > > > > >      pci_bus 0000:00: resource 4 [mem 0xee080000-0xee08ffff]
> > > > > >
> > > > > > Is that intentional?
> > > > >
> > > > > There's also that pci_dbg() in the patch which would show the original
> > > > > addresses (print the resource before setting IORESOURCE_UNSET) but to see
> > > > > it one would need to enable it with dyndbg=... Bjorn was thinking of
> > > > > making that pci_info() though so it would appear always.
> > > > >
> > > > > Was this the entire PCI related diff? I don't see those 0000:00:00.0 BARs
> > > > > getting assigned anywhere.
> > > >
> > > > The above log is almost complete (lacked enabling the device afterwards).
> > > >
> > > > AFAIU, the BARs come from the reg and ranges properties in the
> > > > PCI controller nodes;
> > > > https://elixir.bootlin.com/linux/v6.17/source/arch/arm/boot/dts/renesas/r8a7791.dtsi#L1562
> > >
> > > Thanks, although I had already found this line by grep. I was just
> > > expecting the address appear among root bus resources too.
> > >
> > > Curiously enough, pci_register_host_bridge() seems to try to add some
> > > resource from that list into bus and it's what prints those "root bus
> > > resource" lines and ee090000 is not among the printed lines despite
> > > appearing in /proc/iomem. As is, the resource tree and PCI bus view on the
> > > resources seems to be in disagreement and I'm not sure what to make of it.
> > >
> > > But before considering going into that direction or figuring out why this
> > > ee090000 resource does not appear among root bus resources, could you
> > > check if the attached patch changes behavior for the resource which are
> > > non-zero based?
> >
> > This patch has no impact on dmesg, lspci output, or /proc/iomem
> > for pci-rcar-gen2.
>
> It would have been too easy... :-(
>
> I'm sorry I don't really know these platform well and I'm currently trying
> to understand what adds that ee090000 resource into the resource tree
> and so far I've not been very successful.
>
> Perhaps it would be easiest to print a stacktrace when the resource is
> added but there are many possible functions. I think all of them
> converge in __request_resource() so I suggest adding:
>
> WARN_ON(new->start == 0xee090000);
>
> before __request_resource() does anything.

    Call trace:
     unwind_backtrace from show_stack+0x10/0x14
     show_stack from dump_stack_lvl+0x7c/0xb0
     dump_stack_lvl from __warn+0x80/0x198
     __warn from warn_slowpath_fmt+0xc0/0x124
     warn_slowpath_fmt from __request_resource+0x38/0xc8
     __request_resource from __request_region+0xc4/0x1e8
     __request_region from __devm_request_region+0x80/0xac
     __devm_request_region from __devm_ioremap_resource+0xcc/0x160
     __devm_ioremap_resource from rcar_pci_probe+0x58/0x350
     rcar_pci_probe from platform_probe+0x58/0x90

I.e. the call to devm_platform_get_and_ioremap_resource() in
drivers/pci/controller/pci-rcar-gen2.c:rcar_pci_probe().

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

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