Re: [PATCH v3 1/1] PCI: Fix bug resulting in double hpmemsize being assigned to MMIO window

From: Bjorn Helgaas
Date: Tue Nov 19 2019 - 08:38:34 EST

On Tue, Nov 19, 2019 at 03:17:04AM +0000, Nicholas Johnson wrote:
> I did just discover linux-next and I built it. Should I be doing this
> more often to help find regressions?

Yes, if you build and run linux-next, that's a great service because
it helps find problems before they appear in mainline.

> I will now concentrate on fixing the problem where pci=nocrs does not
> ignore the bus resource. One motherboard I own gives 00-7e or similar,
> instead of 00-ff. The nocrs does not help, and I had to patch the kernel
> myself. Only acpi=off fixes the problem, while knocking out SMT (MADT),
> IOMMU (DMAR) and the ability to suspend without crashing.
> If you disagree that nocrs should override bus resource, then let me
> know and I will not attempt this.

I guess the problem is that with "pci=nocrs", we ignore the MMIO and
I/O port resources from _CRS, but we still pay attention to bus number
resources in _CRS? That does sound like it would be unexpected

I *would* like to see the complete dmesg log because these _CRS
methods are pretty reliable because Windows relies on them as well, so
problems are frequently a result of Linux defects. If we can fix
Linux or automatically work around issues so users don't have to use
"pci=nocrs" explicitly, that's the best.