Subject: Re: Arm64 double PCI ECAM reservations in acpi_resource_consumer()

From: Lorenzo Pieralisi <[email-masked]>
Date: Thu, 3 Jun 2021 15:16:41 +0100

On Wed, Jun 02, 2021 at 08:15:20PM -0400, Qian Cai wrote:
> 
> 
> On 6/2/2021 6:09 PM, Bjorn Helgaas wrote:
> > [+cc linux-pci]
> > 
> > On Wed, Jun 2, 2021 at 4:49 PM Qian Cai <[email-masked]> wrote:
> >>
> >> Bjorn, I noticed PCI ECAM could be reserved twice on arm64. Firs time through,
> >>
> >> [   19.087790][    T1]  acpi_ns_walk_namespace+0xc0/0x390
> >> [   19.092927][    T1]  acpi_get_devices+0x160/0x1a4
> >> [   19.097629][    T1]  acpi_resource_consumer+0x8c/0xc0
> >> [   19.102680][    T1]  pci_acpi_scan_root+0x158/0x4c8
> >> [   19.107555][    T1]  acpi_pci_root_add+0x450/0x8e8
> >> [   19.112345][    T1]  acpi_bus_attach+0x300/0x7d0
> >> [   19.116960][    T1]  acpi_bus_attach+0x178/0x7d0
> >> [   19.121576][    T1]  acpi_bus_attach+0x178/0x7d0
> >> [   19.126190][    T1]  acpi_bus_scan+0xa8/0x170
> >> [   19.130545][    T1]  acpi_scan_init+0x220/0x558
> >> [   19.135074][    T1]  acpi_init+0x1f4/0x270
> >>
> >> where pci_acpi_setup_ecam_mapping() confirmed all reservations are succeed. Then,
> >>
> >> [   19.880588][    T1]  acpi_ns_walk_namespace+0xc0/0x390
> >> [   19.885725][    T1]  acpi_get_devices+0x160/0x1a4
> >> [   19.890426][    T1]  pnpacpi_init+0xa0/0x10
> >>
> >> As the results, those messages are showed up during the boot in pnpacpi_init().
> >>
> >> [ 17.763968] system 00:00: [mem 0x10000000000-0x1000fffffff window] could not be reserved
> >> [ 17.772900] system 00:00: [mem 0x7800000000-0x780fffffff window] could not be reserved
> >> [ 17.781627] system 00:00: [mem 0x7000000000-0x700fffffff window] could not be reserved
> >> [ 17.790350] system 00:00: [mem 0x6000000000-0x600fffffff window] could not be reserved
> >> [ 17.799073] system 00:00: [mem 0x5800000000-0x580fffffff window] could not be reserved
> >> [ 17.808155] system 00:00: [mem 0x1000000000-0x100fffffff window] could not be reserved
> >> [ 17.816862] system 00:00: [mem 0x600000000-0x60fffffff window] could not be reserved
> >> [ 17.825417] system 00:00: [mem 0x400000000-0x40fffffff window] could not be reserved
> >>
> >> Looking through the x86's version of pci_acpi_scan_root(), it won't call acpi_resource_consumer(), so I suppose this bug is only affecting arm64?
> > 
> > This might be related to
> > https://lore.kernel.org/linux-acpi/[email-masked]/T/#u
> > 
> > Can you try applying that patch to see if it is related?
> 
> Unfortunately, that revert patch does not help. FYI, here is the first reservation from acpi_resource_consumer().

This is not the "reservation". AFAICS acpi_resource_consumer() checks
whether the ECAM region is part of _a_ given ACPI device _CRS in the
namespace, it does not "reserve" anything.

IIUC the issue here is that we request the ECAM region in
pci_ecam_create() and later the code in:

drivers/pnp/system.c

tries to request the ECAM region (that lives in the PNP0C02 _CRS) and
fails (see reserve_range() and request_mem_region()).

As the comment in reserve_range() goes, this is harmless, not sure
whether there is anything to do about it.

Lorenzo

> [   16.224306] acpi PNP0A08:00: ECAM area [mem 0x10000000000-0x1000fffffff] reserved by PNP0C02:00
> [   16.241027] acpi PNP0A08:00: ECAM at [mem 0x10000000000-0x1000fffffff] for [bus 00-ff]
> [   16.810172] acpi PNP0A08:01: ECAM area [mem 0x7800000000-0x780fffffff] reserved by PNP0C02:00
> [   16.826701] acpi PNP0A08:01: ECAM at [mem 0x7800000000-0x780fffffff] for [bus 00-ff]
> [   17.289302] acpi PNP0A08:02: ECAM area [mem 0x1000000000-0x100fffffff] reserved by PNP0C02:00
> [   17.305840] acpi PNP0A08:02: ECAM at [mem 0x1000000000-0x100fffffff] for [bus 00-ff]
> [   17.641917] acpi PNP0A08:03: ECAM area [mem 0x5800000000-0x580fffffff] reserved by PNP0C02:00
> [   17.658445] acpi PNP0A08:03: ECAM at [mem 0x5800000000-0x580fffffff] for [bus 00-ff]
> [   18.059837] acpi PNP0A08:04: ECAM area [mem 0x6000000000-0x600fffffff] reserved by PNP0C02:00
> [   18.076368] acpi PNP0A08:04: ECAM at [mem 0x6000000000-0x600fffffff] for [bus 00-ff]
> [   18.413220] acpi PNP0A08:05: ECAM area [mem 0x7000000000-0x700fffffff] reserved by PNP0C02:00
> [   18.429745] acpi PNP0A08:05: ECAM at [mem 0x7000000000-0x700fffffff] for [bus 00-ff]
> [   18.767189] acpi PNP0A08:06: ECAM area [mem 0x600000000-0x60fffffff] reserved by PNP0C02:00
> [   18.783559] acpi PNP0A08:06: ECAM at [mem 0x600000000-0x60fffffff] for [bus 00-ff]
> [   19.201613] acpi PNP0A08:07: ECAM area [mem 0x400000000-0x40fffffff] reserved by PNP0C02:00
> [   19.217965] acpi PNP0A08:07: ECAM at [mem 0x400000000-0x40fffffff] for [bus 00-ff]

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