linux-kernel - Re: Bug report: the extended PCI config space is missed with 6.2-rc2

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Message-ID: <20230105222031.GA1175847@bhelgaas>
Date:   Thu, 5 Jan 2023 16:20:31 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     "Williams, Dan J" <dan.j.williams@...el.com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "kernelorg@...ead.fr" <kernelorg@...ead.fr>,
        "kjhambrick@...il.com" <kjhambrick@...il.com>,
        "2lprbe78@...k.com" <2lprbe78@...k.com>,
        "nicholas.johnson-opensource@...look.com.au" 
        <nicholas.johnson-opensource@...look.com.au>,
        "benoitg@...us.ca" <benoitg@...us.ca>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "wse@...edocomputers.com" <wse@...edocomputers.com>,
        "mumblingdrunkard@...tonmail.com" <mumblingdrunkard@...tonmail.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Box, David E" <david.e.box@...el.com>,
        "Sun, Yunying" <yunying.sun@...el.com>
Subject: Re: Bug report: the extended PCI config space is missed with 6.2-rc2

On Thu, Jan 05, 2023 at 09:49:44PM +0000, Luck, Tony wrote:
> > The EDAC driver wouldn't have any ACPI stuff in it; it's just that
> > Linux is looking for ACPI info about the ECAM area.
> 
> Is there some way for a driver to know that pci_read_config_dword()
> is going to fail for offsets in extended PCIe config space?

There's no nice way to know ahead of time.  "raw_pci_ext_ops ==
&pci_mmcfg" means it should work.  It looks like pci_direct_conf1 and
pci_mmcfg_numachip would also work, but it's all pretty ugly.

You could check the result for PCI_POSSIBLE_ERROR(), since reads
should return ~0 (PCI_ERROR_RESPONSE) if they fail either because we
can't access extended config space or because there was some PCI
error.

Bjorn