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SubjectRe: [PATCH 3/3] x86/PCI: Preserve host bridge windows completely covered by E820
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Hi Bjorn, Rafael,

On 3/5/22 11:37, Hans de Goede wrote:
> Hi,
>
> On 3/4/22 16:46, Hans de Goede wrote:
>> Hi,
>>
>> On 3/4/22 16:32, Bjorn Helgaas wrote:
>>> On Fri, Mar 04, 2022 at 03:16:42PM +0100, Hans de Goede wrote:
>>>> Hi Bjorn,
>>>>
>>>> On 3/4/22 04:51, Bjorn Helgaas wrote:
>>>>> From: Bjorn Helgaas <bhelgaas@google.com>
>>>>>
>>>>> Many folks have reported PCI devices not working. It could affect any
>>>>> device, but most reports are for Thunderbolt controllers on Lenovo Yoga and
>>>>> Clevo Barebone laptops and the touchpad on Lenovo IdeaPads.
>>>>>
>>>>> In every report, a region in the E820 table entirely encloses a PCI host
>>>>> bridge window from _CRS, and because of 4dc2287c1805 ("x86: avoid E820
>>>>> regions when allocating address space"), we ignore the entire window,
>>>>> preventing us from assigning space to PCI devices.
>>>>>
>>>>> For example, the dmesg log [2] from bug report [1] shows:
>>>>>
>>>>> BIOS-e820: [mem 0x000000004bc50000-0x00000000cfffffff] reserved
>>>>> pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window]
>>>>> pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
>>>>>
>>>>> The efi=debug dmesg log [3] from the same report shows the EFI memory map
>>>>> entries that created the E820 map:
>>>>>
>>>>> efi: mem47: [Reserved | |WB|WT|WC|UC] range=[0x4bc50000-0x5fffffff]
>>>>> efi: mem48: [Reserved | |WB| | |UC] range=[0x60000000-0x60ffffff]
>>>>> efi: mem49: [Reserved | | | | | ] range=[0x61000000-0x653fffff]
>>>>> efi: mem50: [MMIO |RUN| | | |UC] range=[0x65400000-0xcfffffff]
>>>>>
>>>>> 4dc2287c1805 ("x86: avoid E820 regions when allocating address space")
>>>>> works around issues where _CRS contains non-window address space that can't
>>>>> be used for PCI devices. It does this by removing E820 regions from host
>>>>> bridge windows. But in these reports, the E820 region covers the entire
>>>>> window, so 4dc2287c1805 makes it completely unusable.
>>>>>
>>>>> Per UEFI v2.8, sec 7.2, the EfiMemoryMappedIO type means:
>>>>>
>>>>> Used by system firmware to request that a memory-mapped IO region be
>>>>> mapped by the OS to a virtual address so it can be accessed by EFI
>>>>> runtime services.
>>>>>
>>>>> A host bridge window is definitely a memory-mapped IO region, and EFI
>>>>> runtime services may need to access it, so I don't think we can argue that
>>>>> this is a firmware defect.
>>>>>
>>>>> Instead, change the 4dc2287c1805 strategy so it only removes E820 regions
>>>>> when they overlap *part* of a host bridge window on the assumption that a
>>>>> partial overlap is really register space, not part of the window proper.
>>>>>
>>>>> If an E820 region covers the entire window from _CRS, assume the _CRS
>>>>> window is correct and do nothing.
>>>>>
>>>>> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1868899
>>>>> [2] https://bugzilla.redhat.com/attachment.cgi?id=1711424
>>>>> [3] https://bugzilla.redhat.com/attachment.cgi?id=1861407
>>>>>
>>>>> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206459
>>>>> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=214259
>>>>> 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
>>>>> Fixes: 4dc2287c1805 ("x86: avoid E820 regions when allocating address space")
>>>>> Link: https://lore.kernel.org/r/20220228105259.230903-1-hdegoede@redhat.com
>>>>> Based-on-patch-by: Hans de Goede <hdegoede@redhat.com>
>>>>> Reported-by: Benoit Grégoire <benoitg@coeus.ca> # BZ 206459
>>>>> Reported-by: wse@tuxedocomputers.com # BZ 214259
>>>>> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>>>>> ---
>>>>> arch/x86/kernel/resource.c | 11 +++++++++++
>>>>> 1 file changed, 11 insertions(+)
>>>>>
>>>>> diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c
>>>>> index 7378ea146976..405f0af53e3d 100644
>>>>> --- a/arch/x86/kernel/resource.c
>>>>> +++ b/arch/x86/kernel/resource.c
>>>>> @@ -39,6 +39,17 @@ void remove_e820_regions(struct device *dev, struct resource *avail)
>>>>> e820_start = entry->addr;
>>>>> e820_end = entry->addr + entry->size - 1;
>>>>>
>>>>> + /*
>>>>> + * If an E820 entry covers just part of the resource, we
>>>>> + * assume E820 is telling us about something like host
>>>>> + * bridge register space that is unavailable for PCI
>>>>> + * devices. But if it covers the *entire* resource, it's
>>>>> + * more likely just telling us that this is MMIO space, and
>>>>> + * that doesn't need to be removed.
>>>>> + */
>>>>> + if (e820_start <= avail->start && avail->end <= e820_end)
>>>>> + continue;
>>>>> +
>>>>
>>>> IMHO it would be good to add some logging here, since hitting this is
>>>> somewhat of a special case. For the Fedora test kernels I did I changed
>>>> this to:
>>>>
>>>> if (e820_start <= avail->start && avail->end <= e820_end) {
>>>> dev_info(dev, "resource %pR fully covered by e820 entry [mem %#010Lx-%#010Lx]\n",
>>>> avail, e820_start, e820_end);
>>>> continue;
>>>> }
>>>>
>>>> And I expect/hope to see this new info message on the ideapad with the
>>>> touchpad issue.
>>>
>>> Right, I would expect the same.
>>>
>>> We could add something like this. But both the e820 entry and the
>>> host bridge window are already in the dmesg log, so it doesn't really
>>> add new information
>>
>> Well it adds the information that the workaround (to the workaround)
>> which we added for this case is working as expected and it allows
>> seeing that is the case in a single glance.
>
> So I just got the first report back from the Fedora test 5.16.12 kernel
> with this series added. Good news on the ideapad this wotks fine to
> fix the touchpad issue (as expected).
>
> What is interesting is that the above dev_info message which I added
> triggers *twice*:
>
> [ 0.327837] acpi PNP0A08:00: resource [mem 0x000a0000-0x000bffff window] fully covered by e820 entry [mem 0x0009f000-0x000fffff]
> [ 0.327843] acpi PNP0A08:00: resource [mem 0x65400000-0xbfffffff window] fully covered by e820 entry [mem 0x4bc50000-0xcfffffff]
>
> Notice that it also stops from the mem-window for ISA io getting fully
> clipped, which I did not realize also was a potential issue.
>
> I hope this also shows that having the dev_info here is good,
> at least IMHO this confirms that having the dev_info for this
> is a good thing.
>
> I'm still waiting for testing results on the X1C2 which had the
> suspend/resume regressions with my bios-date based approach.

I have heard back from the X1C2 user, he does not have access to
the machine atm he will get back to me in a couple of days.

I don't really expect any surprises there though, so given where
we are in the kernel-cycle and that we already have confirmation
that it fixes the ideapad touchpad issues I think we should move
forward with this patch-set now.

Rafael, can you drop my variant of this patch? (this series is
a cleaner implementation of basically the same method to fix
things)

Bjorn, I assume you will merge this series through your tree?

Regards,

Hans

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