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| author |   Hans de Goede <hdegoede@redhat.com> | 2022-05-19 17:21:48 +0200 |
|---|---|---|
| committer |   Bjorn Helgaas <bhelgaas@google.com> | 2022-05-19 14:26:55 -0500 |
| commit | fa6dae5d82081e8d9f8e6a2baf7149442a6c1ba5 (patch) | |
| tree | 0ecf3822a6cf03f3ecdd8f7ba4ae446abacdffbe /Documentation/admin-guide | |
| parent | x86/PCI: Clip only host bridge windows for E820 regions (diff) | |
| download | linux-dev-fa6dae5d82081e8d9f8e6a2baf7149442a6c1ba5.tar.xz linux-dev-fa6dae5d82081e8d9f8e6a2baf7149442a6c1ba5.zip | |
x86/PCI: Add kernel cmdline options to use/ignore E820 reserved regions
Some firmware supplies PCI host bridge _CRS that includes address space
unusable by PCI devices, e.g., space occupied by host bridge registers or
used by hidden PCI devices.
To avoid this unusable space, Linux currently excludes E820 reserved
regions from _CRS windows; see 4dc2287c1805 ("x86: avoid E820 regions when
allocating address space").
However, this use of E820 reserved regions to clip things out of _CRS is
not supported by ACPI, UEFI, or PCI Firmware specs, and some systems have
E820 reserved regions that cover the entire memory window from _CRS.
4dc2287c1805 clips the entire window, leaving no space for hot-added or
uninitialized PCI devices.
For example, from a Lenovo IdeaPad 3 15IIL 81WE:
BIOS-e820: [mem 0x4bc50000-0xcfffffff] reserved
pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window]
pci 0000:00:15.0: BAR 0: [mem 0x00000000-0x00000fff 64bit]
pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit]
Future patches will add quirks to enable/disable E820 clipping
automatically.
Add a "pci=no_e820" kernel command line option to disable clipping with
E820 reserved regions. Also add a matching "pci=use_e820" option to enable
clipping with E820 reserved regions if that has been disabled by default by
further patches in this patch-set.
Both options taint the kernel because they are intended for debugging and
workaround purposes until a quirk can set them automatically.
[bhelgaas: commit log, add printk]
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1868899 Lenovo IdeaPad 3
Link: https://lore.kernel.org/r/20220519152150.6135-2-hdegoede@redhat.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Benoit Grégoire <benoitg@coeus.ca>
Cc: Hui Wang <hui.wang@canonical.com>
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3f1cc5e317ed..2477b639d5c4 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4066,6 +4066,15 @@ please report a bug. nocrs [X86] Ignore PCI host bridge windows from ACPI. If you need to use this, please report a bug. + use_e820 [X86] Use E820 reservations to exclude parts of + PCI host bridge windows. This is a workaround + for BIOS defects in host bridge _CRS methods. + If you need to use this, please report a bug to + <linux-pci@vger.kernel.org>. + no_e820 [X86] Ignore E820 reservations for PCI host + bridge windows. This is the default on modern + hardware. If you need to use this, please report + a bug to <linux-pci@vger.kernel.org>. routeirq Do IRQ routing for all PCI devices. This is normally done in pci_enable_device(), so this option is a temporary workaround |