[Bug 214259] Discrete Thunderbold Controller 8086:1137 throws DMAR and XHCI errors and is only partially functional

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=214259

Bjorn Helgaas (bjorn@helgaas.com) changed:

           What    |Removed                     |Added
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                 CC|                            |bjorn@helgaas.com

--- Comment #25 from Bjorn Helgaas (bjorn@helgaas.com) ---
I don't know the connection to the DMAR faults, but from the first log
(https://bugzilla.kernel.org/attachment.cgi?id=298567):

  BIOS-e820: [mem 0x000000006bc00000-0x00000000efffffff] reserved
  pci_bus 0000:00: root bus resource [mem 0x71000000-0xdfffffff window]

This entire PCI host bridge aperture is "reserved" in the E820 map, which means
we won't allocate any PCI BARs in that area, which means hot-add won't work.

The current workaround for this is https://git.kernel.org/linus/d341838d776a
("x86/PCI: Disable E820 reserved region clipping via quirks"), which appeared
in v5.19.

I think the underlying issue is that this machine has EFI, Linux converts the
EFI memory map to E820 format, and it converts EFI_MEMORY_MAPPED_IO to
E820_TYPE_RESERVED.  EFI_MEMORY_MAPPED_IO means "the OS must map this memory
for use by EFI runtime services."  It does *not* mean "the OS can never use
this memory."  I think Linux should omit EFI_MEMORY_MAPPED_IO areas completely
from the E820 map.

This is basically the same issue as bug #216565.  I attached a patch there to
omit EFI_MEMORY_MAPPED_IO.

I would love to hear from anybody with a Clevo machine that shows similar
problems.  If you can, please boot with the patch at
https://bugzilla.kernel.org/attachment.cgi?id=303123 with the "efi=debug"
kernel parameter, open new bugzilla with the complete dmesg log, and assign it
to me.

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