Re: [PATCH v7 1/1] x86/PCI: Ignore E820 reservations for bridge windows on newer systems

Bjorn Helgaas
2022-05-18T22:08:14Z

On Mon, May 09, 2022 at 07:33:27PM +0200, Hans de Goede wrote:
> On 5/7/22 17:31, Bjorn Helgaas wrote:
>> On Sat, May 07, 2022 at 12:09:03PM +0200, Hans de Goede wrote:
>>> On 5/6/22 18:51, Bjorn Helgaas wrote:
>>>> On Thu, May 05, 2022 at 05:20:16PM +0200, Hans de Goede wrote:
>>>>> Some BIOS-es contain bugs where they add addresses which are already
>>>>> used in some other manner to the PCI host bridge window returned by
>>>>> the ACPI _CRS method. To avoid this Linux by default excludes
>>>>> E820 reservations when allocating addresses since 2010, see:
>>>>> commit 4dc2287c1805 ("x86: avoid E820 regions when allocating address
>>>>> space").
>>>>>
>>>>> Recently (2019) some systems have shown-up with E820 reservations which
>>>>> cover the entire _CRS returned PCI bridge memory window, causing all
>>>>> attempts to assign memory to PCI BARs which have not been setup by the
>>>>> BIOS to fail. For example here are the relevant dmesg bits from a
>>>>> Lenovo IdeaPad 3 15IIL 81WE:
>>>>>
>>>>> [mem 0x000000004bc50000-0x00000000cfffffff] reserved
>>>>> pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window]
>>>>>
>>>>> The ACPI specifications appear to allow this new behavior:
>>>>>
>>>>> The relationship between E820 and ACPI _CRS is not really very clear.
>>>>> ACPI v6.3, sec 15, table 15-374, says AddressRangeReserved means:
>>>>>
>>>>> This range of addresses is in use or reserved by the system and is
>>>>> not to be included in the allocatable memory pool of the operating
>>>>> system's memory manager.
>>>>>
>>>>> and it may be used when:
>>>>>
>>>>> The address range is in use by a memory-mapped system device.
>>>>>
>>>>> Furthermore, sec 15.2 says:
>>>>>
>>>>> Address ranges defined for baseboard memory-mapped I/O devices, such
>>>>> as APICs, are returned as reserved.
>>>>>
>>>>> A PCI host bridge qualifies as a baseboard memory-mapped I/O device,
>>>>> and its apertures are in use and certainly should not be included in
>>>>> the general allocatable pool, so the fact that some BIOS-es reports
>>>>> the PCI aperture as "reserved" in E820 doesn't seem like a BIOS bug.
>>>>>
>>>>> So it seems that the excluding of E820 reserved addresses is a mistake.
>>>>>
>>>>> Ideally Linux would fully stop excluding E820 reserved addresses,
>>>>> but then various old systems will regress.
>>>>> Instead keep the old behavior for old systems, while ignoring
>>>>> the E820 reservations for any systems from now on.
>>>>>
>>>>> Old systems are defined here as BIOS year < 2018, this was chosen to
>>>>> make sure that pci_use_e820 will not be set on the currently affected
>>>>> systems, the oldest known one is from 2019.
>>>>>
>>>>> Testing has shown that some newer systems also have a bad _CRS return.
>>>>> The pci_crs_quirks DMI table is used to keep excluding E820 reservations
>>>>> from the bridge window on these systems.
>>>>>
>>>>> Also add pci=no_e820 and pci=use_e820 options to allow overriding
>>>>> the BIOS year + DMI matching logic.
>>>>>
>>>>> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206459
>>>>> BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1868899
>>>>> BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1871793
>>>>> BugLink: https://bugs.launchpad.net/bugs/1878279
>>>>> BugLink: https://bugs.launchpad.net/bugs/1931715
>>>>> BugLink: https://bugs.launchpad.net/bugs/1932069
>>>>> BugLink: https://bugs.launchpad.net/bugs/1921649
>>>>> Cc: Benoit Grégoire <benoitg@coeus.ca>
>>>>> Cc: Hui Wang <hui.wang@canonical.com>
>>>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>>>
>>>>> + * Ideally Linux would fully stop using E820 reservations, but then
>>>>> + * various old systems will regress. Instead keep the old behavior for
>>>>> + * old systems + known to be broken newer systems in pci_crs_quirks.
>>>>> + */
>>>>> + if (year >= 0 && year < 2018)
>>>>> + pci_use_e820 = true;
>>>>
>>>> How did you pick 2018? Prior to this patch, we used E820 reservations
>>>> for all machines. This patch would change that for 2019-2022
>>>> machines, so there's a risk of breaking some of them.
>>>
>>> Correct. I picked 2018 because the first devices where using E820
>>> reservations are causing issues (i2c controller not getting resources
>>> leading to non working touchpad / thunderbolt hotplug issues) have
>>> BIOS dates starting in 2019. I added a year margin, so we could make
>>> this 2019.
>>>
>>>> I'm hesitant about changing the behavior for machines already in the
>>>> field because if they were tested at all with Linux, it was without
>>>> this patch. So I would lean toward preserving the current behavior
>>>> for BIOS year < 2023.
>>>
>>> I see, I presume the idea is to then use DMI to disable E820 clipping
>>> on current devices where this is known to cause problems ?
>>>
>>> So for v8 I would:
>>>
>>> 1. Change the cut-off check to < 2023
>>> 2. Drop the DMI quirks I added for models which are known to need E820
>>> clipping hit by the < 2018 check
>>> 3. Add DMI quirks for models for which it is known that we must _not_
>>> do E820 clipping
>>>
>>> Is this the direction you want to go / does that sound right?
>>
>> Yes, I think that's what we should do. All the machines in the field
>> will be unaffected, except that we add quirks for known problems.
>
> I've been working on this today. I've mostly been going through
> the all the existing bugs about this, to make a list of DMI matches
> for devices on which we should _not_ do e820 clipping to fix th
> kernel being unable to assign BARs there.
>
> I've found an interesting pattern there, all affected devices
> are Lenovo devices with "IIL" in there device name, e.g. :
> "IdeaPad 3 15IIL05". I've looked up all Lenovo devices which
> have "IIL" as part of their DMI_PRODUCT_VERSION string here:
> https://github.com/linuxhw/DMI/
>
> And then looked them up at https://linux-hardware.org/ and checked
> their dmesg to see if they have the e820 problem other ideapads
> have. I've gone through approx. half the list now and all
> except one model seem to have the e820 problem.
>
> So it looks like we might be able to match all problem models
> with a single DMI match.
>

> So the problem seems to be limited to one specific device
> series / range and this is making me have second thoughts
> about doing a date based cut-off at all. Trying to switch
> over any models which are new in 2023 is fine, the problem
> with a DMI BIOS date approach though is that as soon as some
> new management-engine CVE comes out we will also see BIOS
> updates with a year of 2023 for many existing models, of
> up to 3-4 years old at least; and chances are that some of
> those older models getting BIOS updates will be bitten by
> this change.
>
> So as said I'm having second thoughts about the date based
> approach. Bjorn, what do you think of just using DMI quirks
> to disable e820 clipping on known problematic models and
> otherwise keeping things as is ?

The current v8 patch [1] adds quirks to disable clipping for Lenovo
"*IIL*" and Acer Spin 5. I think we also need to add one for Clevo
Barebones [2], don't we?

Here's how I think about the date-based approach. See if it seems
sensible to you.

Without a date check, we'll continue clipping by default:

- Future systems like Lenovo *IIL*, Acer Spin, and Clevo Barebones
will require new quirks to disable clipping.

- The problem here is E820 entries that cover entire _CRS windows
that should not be clipped out.

- I think these E820 entries are legal per spec, and it would be
hard to get BIOS vendors to change them.

- We will discover new systems that need clipping disabled piecemeal
as they are released.

- Future systems like Lenovo X1 Carbon and the Chromebooks (probably
anything using coreboot) will just work and we will not notice new
ones that rely on the clipping.

- BIOS updates will not require new quirks unless they change the
DMI model string.

With a date check that disables clipping, e.g., "no clipping when
date > 2022":

- Future systems like Lenovo *IIL*, Acer Spin, and Clevo Barebones
will just work without new quirks.

- Future systems like Lenovo X1 Carbon and the Chromebooks will
require new quirks to *enable* clipping.

- The problem here is that _CRS contains regions that are not usable
by PCI devices, and we rely on the E820 kludge to clip them out.

- I think this use of E820 is clearly a firmware bug, so we have a
fighting chance of getting it changed eventually.

- BIOS updates after the cutoff date *will* require quirks, but only
for systems like Lenovo X1 Carbon and Chromebooks that we already
think have broken firmware.

Is that a fair summary?

If so, it still seems to me like it's better to add quirks for
firmware that we think is broken than for firmware that seems unusual
but correct.

But I do think maybe we should split the date check to a separate
patch. The rationale for the date check (to put the quirk burden on
systems with buggy firmware) is a little different from the "disable
E820 clipping" reason for the quirks.

I think the "disable clipping" quirks by themselves should fix all the
known broken systems, shouldn't they? I'd really, really like to get
these quirks in for v5.18 if possible.

For future reference, I'm attaching below all the bugs I know about
and the details of what's in E820 and _CRS.

Bjorn

[1] https://lore.kernel.org/r/20220512202511.34197-1-hdegoede@redhat.com
[2] https://bugzilla.kernel.org/show_bug.cgi?id=214259

https://bugzilla.kernel.org/show_bug.cgi?id=16228 Dell Precision T3500
BIOS-e820: 0xbfe4dc00-0xc0000000 (reserved)
pci_root PNP0A03:00: host bridge window [mem 0xbff00000-0xdfffffff]
pci 0000:00:1f.2: BAR 5: assigned [mem 0xbff00000-0xbff007ff]
ahci 0000:00:1f.2: controller reset failed (0xffffffff)
E820 covers part of _CRS window, 4dc2287c1805 clips that out.
Without 4dc2287c1805, doesn't boot because AHCI at
[mem 0xbff00000-0xbff007ff] is unusable.

https://bugzilla.kernel.org/show_bug.cgi?id=206459 Lenovo Yoga C940-14IIL
DMI: LENOVO 81Q9/LNVNB161216, BIOS AUCN54WW 01/09/2020
BIOS-e820: [mem 0x4bc50000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window]
pci 0000:2b:00.0: BAR 14: no space for [mem size 0x0c200000]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, Thunderbolt dock hot-add can't allocate MMIO
space.

https://bugzilla.kernel.org/show_bug.cgi?id=214259 Clevo X170KM Barebone
DMI: TUXEDO TUXEDO Book XUX7 - Gen12/X170KM-G, BIOS 1.07.05RTR1 02/01/2021
BIOS-e820: [mem 0x6bc00000-0xefffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x71000000-0xdfffffff window]
BIOS-e820: [mem 0x0100000000-0x48effffff] usable
pci_bus 0000:00: root bus resource [mem 0x4000000000-0x7fffffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit] # intel-lpss
pci 0000:00:15.1: reg 0x10: [mem 0x00000000-0x00000fff 64bit] # intel-lpss
pci 0000:00:15.2: reg 0x10: [mem 0x00000000-0x00000fff 64bit] # intel-lpss
pci 0000:00:19.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit] # intel-lpss
pci 0000:00:1f.5: reg 0x10: [mem 0xfe010000-0xfe010fff] # intel_spi_pci, no window
pci 0000:00:15.0: BAR 0: assigned [mem 0x420210f000-0x420210ffff 64bit]
pci 0000:00:15.1: BAR 0: assigned [mem 0x4202111000-0x4202111fff 64bit]
pci 0000:00:15.2: BAR 0: assigned [mem 0x4202112000-0x4202112fff 64bit]
pci 0000:00:19.0: BAR 0: assigned [mem 0x4202113000-0x4202113fff 64bit]
pci 0000:00:1f.5: BAR 0: no space for [mem size 0x00001000]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.

https://bugzilla.redhat.com/show_bug.cgi?id=1868899 Lenovo IdeaPad 3 15IIL05
DMI: LENOVO 81WE/LNVNB161216, BIOS EMCN44WW 12/23/2020
BIOS-e820: [mem 0x4bc50000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken (BIOS didn't assign, no space to
allocate).

https://bugzilla.redhat.com/show_bug.cgi?id=1871793 Lenovo IdeaPad 5 14IIL05
DMI: LENOVO 81YH/LNVNB161216, BIOS DSCN22WW(V1.08) 03/06/2020
BIOS-e820: [mem 0x5bc50000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x6d400000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken (BIOS didn't assign, no space to
allocate).

https://bugzilla.redhat.com/show_bug.cgi?id=2029207 Lenovo X1 Carbon (20A7)
DMI: LENOVO 20A7008CUK/20A7008CUK, BIOS GRET63WW (1.40 ) 03/27/2020
BIOS-e820: [mem 0xdceff000-0xdfa0ffff] reserved
pci_bus 0000:00: root bus resource [mem 0xdfa00000-0xfebfffff window]
pci 0000:00:1c.0: BAR 14: assigned [mem 0xdfa00000-0xdfbfffff]
E820 covers part of _CRS window, 4dc2287c1805 clips that out.
Without 4dc2287c1805, doesn't wake from suspend because
[mem 0xdfa00000-0xdfa0ffff] unusable.

https://bugs.launchpad.net/bugs/1878279 Lenovo IdeaPad 5 14IIL05
DMI: LENOVO 81YH/LNVNB161216, BIOS DSCN23WW(V1.09) 03/25/2020
BIOS-e820: [mem 0x5bc50000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x6d400000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken (BIOS didn't assign, no space to
allocate).

https://bugs.launchpad.net/bugs/1880172 Lenovo IdeaPad 3 14IIL05 Core i3-1005G1 (81WD004MGE)
DMI: LENOVO 81WD/LNVNB161216, BIOS EMCN13WW 03/06/2020
BIOS-e820: [mem 0x6b000000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x70400000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken (BIOS didn't assign, no space to
allocate).

https://bugs.launchpad.net/bugs/1884232 Acer Spin SP513-54N
DMI: Acer Spin SP513-54N/Caboom_IL, BIOS V1.00 02/21/2020
BIOS-e820: [mem 0x39e00000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x3f800000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken (BIOS didn't assign, no space to
allocate).

https://bugs.launchpad.net/bugs/1921649 Lenovo IdeaPad S145 82DJ0000BR
DMI: LENOVO 82DJ/LNVNB161216, BIOS DKCN48WW 07/22/2020
BIOS-e820: [mem 0x6b000000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x70400000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken (BIOS didn't assign, no space to
allocate).

https://bugs.launchpad.net/bugs/1931715 Lenovo IdeaPad S145 82DJ0001BR
DMI: LENOVO 82DJ/LNVNB161216, BIOS DKCN51WW 12/23/2020
BIOS-e820: [mem 0x6b000000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x70400000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken, no dmesg from broken case.

https://bugs.launchpad.net/bugs/1932069 Lenovo BS145-15IIL
DMI: LENOVO 82HB/LNVNB161216, BIOS DKCN51WW 12/23/2020
BIOS-e820: [mem 0x4bc50000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window]
pci 0000:00:15.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
E820 covers entire _CRS window. 4dc2287c1805 clips it all out.
With 4dc2287c1805, touchpad broken (BIOS didn't assign, no space to
allocate).

https://lore.kernel.org/r/4e9fca2f-0af1-3684-6c97-4c35befd5019@redhat.com
Google internal report b/148759816
Chromebook asus-C523NA-A20057-coral
BIOS-e820: [mem 0x7b000000-0x7fffffff] reserved
BIOS-e820: [mem 0xd0000000-0xd0ffffff]
acpi PNP0A08:00: ... [mem 0x7b800000-0x7fffffff window] ...
acpi PNP0A08:00: ... [mem 0x80000000-0xe0000000 window] ...
pci_bus 0000:00: root bus resource [mem 0x7b800000-0xe0000000 window]
E820 covers [mem 0x7b800000-0x7fffffff] of _CRS window.
E820 punches [mem 0xd0000000-0xd0ffffff] hole for hidden device.
4dc2287c1805 clips these out. Without 4dc2287c1805, boot fails.
Hidden device is a landmine unless we trim it out.

But 4c5e242d3e93 ("x86/PCI: Clip only host bridge windows for E820
regions") changes the time at which clipping is done.

If clipping preserves resources *completely* covered by E820, and we
clip *before* coalescing, [mem 0x7b800000-0x7fffffff window] is
preserved and [mem 0xd0000000-0xd0ffffff] is clipped out, resulting
in [mem 0x7b800000-0xcfffffff window], where 0x7b800000-0x7fffffff is
not usable.

If clipping preserves resources *completely* covered by E820, and we
clip *after* coalescing, we clip out [mem 0x7b000000-0x7fffffff]
and [mem 0xd0000000-0xd0ffffff], resulting in [mem
0x80000000-0xcfffffff window], which is usable.

Chromebook hp-x360-12b-n4000-octopus similar to asus-C523NA-A20057-coral

Summary:
These are broken by 4dc2287c1805:
https://bugzilla.kernel.org/show_bug.cgi?id=206459 01/09/2020 LENOVO
https://bugzilla.redhat.com/show_bug.cgi?id=1868899 12/23/2020 LENOVO
https://bugzilla.redhat.com/show_bug.cgi?id=1871793 03/06/2020 LENOVO
https://bugs.launchpad.net/bugs/1878279 03/25/2020 LENOVO
https://bugs.launchpad.net/bugs/1880172 03/06/2020 LENOVO
https://bugs.launchpad.net/bugs/1884232 02/21/2020 Acer
https://bugs.launchpad.net/bugs/1921649 07/22/2020 LENOVO
https://bugs.launchpad.net/bugs/1931715 12/23/2020 LENOVO
https://bugs.launchpad.net/bugs/1932069 12/23/2020 LENOVO
For all of the above, E820 covers entire _CRS window. Trimming
the entire window means we can't assign any MMIO space.

These require 4dc2287c1805:
https://bugzilla.kernel.org/show_bug.cgi?id=16228 03/09/2009 Dell
https://bugzilla.redhat.com/show_bug.cgi?id=2029207 03/27/2020 LENOVO
b/148759816 Chromebooks
For the above, E820 covers part of _CRS window. Failure to trim
that part means we assign MMIO space that doesn't work.