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

[Bjorn Helgaas <helgaas@kernel.org>]

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@linux.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.

Bjorn