linux-kernel - Re: [PATCH v4] PCI: of: Clear 64-bit flag for non-prefetchable memory below 4GB

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Message-ID: <YMyl31ERhGDE1yGh@m4>
Date:   Fri, 18 Jun 2021 15:55:43 +0200
From:   Domenico Andreoli <domenico.andreoli@...ux.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Punit Agrawal <punitagrawal@...il.com>, robh+dt@...nel.org,
        maz@...nel.org, leobras.c@...il.com,
        linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, alexandru.elisei@....com, wqu@...e.com,
        robin.murphy@....com, pgwipeout@...il.com, ardb@...nel.org,
        briannorris@...omium.org, shawn.lin@...k-chips.com,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v4] PCI: of: Clear 64-bit flag for non-prefetchable
 memory below 4GB

On Wed, Jun 16, 2021 at 06:12:34PM -0500, Bjorn Helgaas wrote:
> On Tue, Jun 15, 2021 at 08:04:57AM +0900, Punit Agrawal wrote:
> > Alexandru and Qu reported this resource allocation failure on
> > ROCKPro64 v2 and ROCK Pi 4B, both based on the RK3399:
> > 
> >   pci_bus 0000:00: root bus resource [mem 0xfa000000-0xfbdfffff 64bit]
> >   pci 0000:00:00.0: PCI bridge to [bus 01]
> >   pci 0000:00:00.0: BAR 14: no space for [mem size 0x00100000]
> >   pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x00003fff 64bit]
> > 
> > "BAR 14" is the PCI bridge's 32-bit non-prefetchable window, and our
> > PCI allocation code isn't smart enough to allocate it in a host
> > bridge window marked as 64-bit, even though this should work fine.
> > 
> > A DT host bridge description includes the windows from the CPU
> > address space to the PCI bus space.  On a few architectures
> > (microblaze, powerpc, sparc), the DT may also describe PCI devices
> > themselves, including their BARs.
> > 
> > Before 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource
> > flags for 64-bit memory addresses"), of_bus_pci_get_flags() ignored
> > the fact that some DT addresses described 64-bit windows and BARs.
> > That was a problem because the virtio virtual NIC has a 32-bit BAR
> > and a 64-bit BAR, and the driver couldn't distinguish them.
> > 
> > 9d57e61bf723 set IORESOURCE_MEM_64 for those 64-bit DT ranges, which
> > fixed the virtio driver.  But it also set IORESOURCE_MEM_64 for host
> > bridge windows, which exposed the fact that the PCI allocator isn't
> > smart enough to put 32-bit resources in those 64-bit windows.
> > 
> > Clear IORESOURCE_MEM_64 from host bridge windows since we don't need
> > that information.
> > 
> > Fixes: 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource flags for 64-bit memory addresses")
> > Reported-at: https://lore.kernel.org/lkml/7a1e2ebc-f7d8-8431-d844-41a9c36a8911@arm.com/
> > Reported-by: Alexandru Elisei <alexandru.elisei@....com>
> > Reported-by: Qu Wenruo <wqu@...e.com>
> > Suggested-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > Signed-off-by: Punit Agrawal <punitagrawal@...il.com>
> > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > Cc: Rob Herring <robh+dt@...nel.org>
> 
> Applied with:
> 
>     Tested-by: Alexandru Elisei <alexandru.elisei@....com>
>     Reviewed-by: Rob Herring <robh@...nel.org>
>     Acked-by: Ard Biesheuvel <ardb@...nel.org>
> 
> to for-linus for v5.13, thanks a lot!

Late-tested-by: Domenico Andreoli <domenico.andreoli@...ux.com>

See https://lore.kernel.org/lkml/YMyTUv7Jsd89PGci@m4/T/#u

Thanks!

Dom

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