linux-kernel - Re: [PATCH v1 1/1] x86/PCI: Disable e820 usage for the resource allocation

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Date:   Tue, 14 Jun 2022 17:45:38 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ferry Toth <ftoth@...londelft.nl>
Subject: Re: [PATCH v1 1/1] x86/PCI: Disable e820 usage for the resource allocation

On Tue, Jun 14, 2022 at 5:26 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Tue, Jun 14, 2022 at 02:55:42PM +0300, Andy Shevchenko wrote:
> > On Mon, Jun 13, 2022 at 05:35:20PM -0500, Bjorn Helgaas wrote:
> > > On Mon, Jun 13, 2022 at 11:16:41PM +0300, Andy Shevchenko wrote:
> > > > The resource management improve for PCI on x86 broke booting of Intel MID
> > > > platforms. It seems that the current code removes all available resources
> > > > from the list and none of the PCI device may be initialized. Restore the
> > > > old behaviour by force disabling the e820 usage for the resource allocation.
> > > >
> > > > Fixes: 4c5e242d3e93 ("x86/PCI: Clip only host bridge windows for E820 regions")
> > > > Depends-on: fa6dae5d8208 ("x86/PCI: Add kernel cmdline options to use/ignore E820 reserved regions")
> > > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > >
> > > Yeah, I blew it with 4c5e242d3e93.  Can you provide more details on
> > > how the MID platforms broke?
> >
> > It's not so easy. The breakage seems affects the console driver and earlycon
> > doesn't work. erlyprintk doesn't support 32-bit MMIO addresses (again,
> > addresses, not data size). That said, there is nothing to show at all.
> >
> > What I did, I have bisected to your patch, commented out the call and instead
> > added a printk() to see what it does, and it basically removed all resources
> > listed in _CRS.
> >
> > > Since you set "pci_use_e820 = false" for
> > > MID below, I assume MID doesn't depend on the e820 clipping and thus
> > > should not break if we turn off clipping by default in 2023 as in
> > > 0ae084d5a674 ("x86/PCI: Disable E820 reserved region clipping starting
> > > in 2023").
> >
> > > But it'd be nice to see the dmesg log and make sure.
> >
> > Nothing to provide (see above why), sorry.
>
> A dmesg log with a working kernel, especially from one with Hans'
> revert, which might have a little more logging about clipping, might
> have enough info to help figure this out.

https://paste.debian.net/1244105/

(It has a lot of unrelated debug thingy, sorry I didn't cut that out)

-- 
With Best Regards,
Andy Shevchenko