linux-kernel - Re: [PATCH v2 0/7] PCI: Solve two bridge window sizing issues

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Date: Thu, 18 Jan 2024 11:27:41 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Jonathan Woithe <jwoithe@...t42.net>
cc: Igor Mammedov <imammedo@...hat.com>, linux-pci@...r.kernel.org, 
    Bjorn Helgaas <bhelgaas@...gle.com>, 
    Lorenzo Pieralisi <lorenzo.pieralisi@....com>, 
    Rob Herring <robh@...nel.org>, 
    Krzysztof Wilczyński <kw@...ux.com>, 
    Lukas Wunner <lukas@...ner.de>, 
    Mika Westerberg <mika.westerberg@...ux.intel.com>, 
    Andy Shevchenko <andriy.shevchenko@...el.com>, 
    "Rafael J . Wysocki" <rafael@...nel.org>, 
    LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/7] PCI: Solve two bridge window sizing issues

On Thu, 18 Jan 2024, Jonathan Woithe wrote:

> On Thu, Jan 11, 2024 at 06:30:22PM +1030, Jonathan Woithe wrote:
> > On Thu, Jan 04, 2024 at 10:48:53PM +1030, Jonathan Woithe wrote:
> > > On Thu, Jan 04, 2024 at 01:12:10PM +0100, Igor Mammedov wrote:
> > > > On Thu, 28 Dec 2023 18:57:00 +0200
> > > > Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com> wrote:
> > > > 
> > > > > Hi all,
> > > > > 
> > > > > Here's a series that contains two fixes to PCI bridge window sizing
> > > > > algorithm. Together, they should enable remove & rescan cycle to work
> > > > > for a PCI bus that has PCI devices with optional resources and/or
> > > > > disparity in BAR sizes.
> > > > > 
> > > > > For the second fix, I chose to expose find_empty_resource_slot() from
> > > > > kernel/resource.c because it should increase accuracy of the cannot-fit
> > > > > decision (currently that function is called find_resource()). In order
> > > > > to do that sensibly, a few improvements seemed in order to make its
> > > > > interface and name of the function sane before exposing it. Thus, the
> > > > > few extra patches on resource side.
> > > > > 
> > > > > Unfortunately I don't have a reason to suspect these would help with
> > > > > the issues related to the currently ongoing resource regression
> > > > > thread [1].
> > > > 
> > > > Jonathan,
> > > > can you test this series on affected machine with broken kernel to see if
> > > > it's of any help in your case?
> > > 
> > > Certainly, but it will have to wait until next Thursday (11 Jan 2024).  I'm
> > > still on leave this week, and when at work I only have physical access to
> > > the machine concerned on Thursdays at present.
> > > 
> > > Which kernel would you prefer I apply the series to?
> > 
> > I was very short of time today but I did apply the above series to the
> > 5.15.y branch (since I had this source available), resulting in version
> > 5.15.141+.  Unfortunately, in the rush I forgot to do a clean after the
> > bisect reset, so the resulting kernel was not correctly built.  It booted
> > but thought it was a different version and therefore none of the modules
> > could be found.  As a result, the test is invalid.
> > 
> > I will try again in a week when I next have physical access to the system. 
> > Apologies for the delay.  In the meantime, if there's a specific kernel I
> > should apply the patch series against please let me know.  As I understand
> > it, you want it applied to one of the kernels which failed, making 5.15.y
> > (for y < 145) a reasonable choice.
> 
> I did a "make clean" to reset the source tree and recompiled.  However, it
> errored out:
> 
>   drivers/pci/setup-bus.c:988:24: error: ‘RESOURCE_SIZE_MAX’ undeclared
>   drivers/pci/setup-bus.c:998:17: error: ‘pci_bus_for_each_resource’ undeclared
> 
> This was with the patch series applied against 5.15.141.  It seems the patch
> targets a kernel that's too far removed from 5.15.x.
> 
> Which kernel would you like me to apply the patch series to and test?

Two argument version of pci_bus_for_each_resource() is quite new (so 
either 6.6 or 6.7). If want to attempt to compile in 5.15.x, you need 
this:

include/linux/limits.h:#define RESOURCE_SIZE_MAX        ((resource_size_t)~0)

And to add one extra argument into pci_bus_for_each_resource(bus, r) in 
pbus_upstream_assigned_limit():

	...
	while ((bus = bus->parent)) {
+		unsigned int i;
		if (pci_is_root_bus(bus))
			break;

-		pci_bus_for_each_resource(bus, r) {
+		pci_bus_for_each_resource(bus, r, i) {

Note I've written this "patch" by hand inline so patch command cannot 
apply it but you need to edit those in.


-- 
 i.