linux-kernel - Re: [PATCH 1/1] PCI: Do not size non-existing prefetchable window

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Message-ID: <4419385c114b344ba5c1d5b0a817a322b37624cc.camel@gmail.com>
Date: Mon, 27 Oct 2025 18:45:43 +0100
From: Klaus Kudielka <klaus.kudielka@...il.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,  Bjorn
 Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] PCI: Do not size non-existing prefetchable window

On Mon, 2025-10-27 at 15:24 +0200, Ilpo Järvinen wrote:
> pbus_size_mem() should only be called for bridge windows that exist but
> __pci_bus_size_bridges() may point 'pref' to a resource that does not
> exist (has zero flags) in case of non-root buses.
> 
> When prefetchable bridge window does not exist, the same
> non-prefetchable bridge window is sized more than once which may result
> in duplicating entries into the realloc_head list. Duplicated entries
> are shown in this log and trigger a WARN_ON() because realloc_head had
> residual entries after the resource assignment algorithm:
> 
> pci 0000:00:03.0: [11ab:6820] type 01 class 0x060400 PCIe Root Port
> pci 0000:00:03.0: PCI bridge to [bus 00]
> pci 0000:00:03.0:   bridge window [io  0x0000-0x0fff]
> pci 0000:00:03.0:   bridge window [mem 0x00000000-0x000fffff]
> pci 0000:00:03.0: bridge window [mem 0x00200000-0x003fffff] to [bus 02] add_size 200000 add_align 200000
> pci 0000:00:03.0: bridge window [mem 0x00200000-0x003fffff] to [bus 02] add_size 200000 add_align 200000
> pci 0000:00:03.0: bridge window [mem 0xe0000000-0xe03fffff]: assigned
> pci 0000:00:03.0: PCI bridge to [bus 02]
> pci 0000:00:03.0:   bridge window [mem 0xe0000000-0xe03fffff]
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1 at drivers/pci/setup-bus.c:2373 pci_assign_unassigned_root_bus_resources+0x1bc/0x234

With this patch on top of v6.18-rc3, the boot log looks clean again:

pci 0000:00:03.0: [11ab:6820] type 01 class 0x060400 PCIe Root Port
pci 0000:00:03.0: PCI bridge to [bus 00]
pci 0000:00:03.0:   bridge window [io  0x0000-0x0fff]
pci 0000:00:03.0:   bridge window [mem 0x00000000-0x000fffff]
pci 0000:00:03.0: bridge configuration invalid ([bus 00-00]), reconfiguring
pci 0000:00:03.0: bridge window [mem 0x00200000-0x003fffff] to [bus 02] add_size 200000 add_align 200000
pci 0000:00:03.0: bridge window [mem 0xe0000000-0xe03fffff]: assigned
pci 0000:00:03.0: PCI bridge to [bus 02]
pci 0000:00:03.0:   bridge window [mem 0xe0000000-0xe03fffff]

(and no WARNING thereafter)
Thanks a lot!

Tested-by: Klaus Kudielka <klaus.kudielka@...il.com>