[PATCH v8 0/1] x86/PCI: Ignore E820 reservations for bridge windows on future systems

[PATCH v8 0/1] x86/PCI: Ignore E820 reservations for bridge windows on future systems

[Hans de Goede]

Hi All,

Here is v8 of my patch to address the E820 reservations vs PCI host bridge
ranges issue which are causing touchpad and/or thunderbolt issues on many
different laptop models.

After previous attemps to identify these systems by looking for E820
reservations covering the entire bridge window, which broke the boot
on some coreboot based ChromeBooks we are now back to using a bios date
based approach.

Changes in v8:
- Change the cut-off for no longer excluding E820 reservations from
  the bridge window to BIOS year >= 2023 so that this only applies to
  upcoming systems.
- Use DMI quirks for existing systems on which excluding E820
  reservations from the _CRS returned bridge window is an issue.

This is based on top of Bjorn's pci/resource branch:
https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/log/?h=pci/resource

Regards,

Hans


Hans de Goede (1):
  x86/PCI: Ignore E820 reservations for bridge windows on future systems

 .../admin-guide/kernel-parameters.txt         |   9 ++
 arch/x86/include/asm/pci_x86.h                |   2 +
 arch/x86/pci/acpi.c                           | 109 +++++++++++++++++-
 arch/x86/pci/common.c                         |   8 ++
 4 files changed, 126 insertions(+), 2 deletions(-)

-- 
2.36.0

[PATCH v8 1/1] x86/PCI: Ignore E820 reservations for bridge windows on future systems

[Hans de Goede]

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 future
systems.

That is ignore E820 reservations starting with systems with
a DMI BIOS year >= 2023.

And use DMI quirks for existing systems on which excluding E820
reservations from the _CRS returned bridge window is an issue.

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/1880172
BugLink: https://bugs.launchpad.net/bugs/1884232
BugLink: https://bugs.launchpad.net/bugs/1921649
BugLink: https://bugs.launchpad.net/bugs/1931715
BugLink: https://bugs.launchpad.net/bugs/1932069
Cc: Benoit Grégoire <benoitg@coeus.ca>
Cc: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v8:
- Change the cut-off for no longer excluding E820 reservations from
  the bridge window to BIOS year >= 2023 so that this only applies to
  upcoming systems.
- Use DMI quirks for existing systems on which excluding E820
  reservations from the _CRS returned bridge window is an issue.

Changes in v7:
- Re-add the pci=use_e820 and pci=no_e820 kernel cmdline options since it
  turns out that some newer laptops still need pci=use_e820
- Add DMI quirks for known newer laptops which need pci=use_e820

Changes in v6:
- Remove the possibility to change the behavior from the commandline
  because of worries that users may use this to paper over other problems

Changes in v5:
- Drop mention of Windows behavior from the commit msg, replace with a
  reference to the specs
- Improve documentation in Documentation/admin-guide/kernel-parameters.txt
- Reword the big comment added, use "PCI host bridge window" in it and drop
  all refences to Windows

Changes in v4:
- Rewrap the big comment block to fit in 80 columns
- Add Rafael's Acked-by
- Add Cc: stable@vger.kernel.org

Changes in v3:
- Commit msg tweaks (drop dmesg timestamps, typo fix)
- Use "defined(CONFIG_...)" instead of "defined CONFIG_..."
- Add Mika's Reviewed-by

Changes in v2:
- Replace the per model DMI quirk approach with disabling E820 reservations
  checking for all systems with a BIOS year >= 2018
- Add documentation for the new kernel-parameters to
  Documentation/admin-guide/kernel-parameters.txt
---
 .../admin-guide/kernel-parameters.txt         |   9 ++
 arch/x86/include/asm/pci_x86.h                |   2 +
 arch/x86/pci/acpi.c                           | 109 +++++++++++++++++-
 arch/x86/pci/common.c                         |   8 ++
 4 files changed, 126 insertions(+), 2 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
diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
index a0627dfae541..ce3fd3311772 100644
--- a/arch/x86/include/asm/pci_x86.h
+++ b/arch/x86/include/asm/pci_x86.h
@@ -42,6 +42,8 @@ do {						\
 #define PCI_ROOT_NO_CRS		0x100000
 #define PCI_NOASSIGN_BARS	0x200000
 #define PCI_BIG_ROOT_WINDOW	0x400000
+#define PCI_USE_E820		0x800000
+#define PCI_NO_E820		0x1000000
 
 extern unsigned int pci_probe;
 extern unsigned long pirq_table_addr;
diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index 562c81a51ea0..125c55b58d7e 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -20,6 +20,7 @@ struct pci_root_info {
 #endif
 };
 
+static bool pci_use_e820 = true;
 static bool pci_use_crs = true;
 static bool pci_ignore_seg;
 
@@ -42,6 +43,13 @@ static int __init set_ignore_seg(const struct dmi_system_id *id)
 	return 0;
 }
 
+static int __init set_no_e820(const struct dmi_system_id *id)
+{
+	printk(KERN_INFO "PCI: %s detected: ignoring e820 regions\n", id->ident);
+	pci_use_e820 = false;
+	return 0;
+}
+
 static const struct dmi_system_id pci_crs_quirks[] __initconst = {
 	/* http://bugzilla.kernel.org/show_bug.cgi?id=14183 */
 	{
@@ -136,6 +144,74 @@ static const struct dmi_system_id pci_crs_quirks[] __initconst = {
 			DMI_MATCH(DMI_PRODUCT_NAME, "HP xw9300 Workstation"),
 		},
 	},
+
+	/*
+	 * Most Lenovo models with "IIL" in their DMI_PRODUCT_VERSION have
+	 * an E820 reservation which covers the entire _CRS returned 32 bit
+	 * PCI bridge memory window, causing all attempts to assign memory to
+	 * 32 bit PCI bars which have not been setup by the BIOS to fail.
+	 * Specifically this often causes some of the I2C controllers to not
+	 * work breaking touchpad support and/or this may cause issues when
+	 * hotplugging thunderbolt connected devices.
+	 *
+	 * This DMI match entry covers the following DMI_PRODUCT_VERSION-s with
+	 * an E820 reservation which covers the entire 32 bit bridge window:
+	 * "IdeaPad 3 14IIL05", "IdeaPad 3 15IIL05", "IdeaPad 3 17IIL05",
+	 * "IdeaPad 5 14IIL05", "IdeaPad 5 15IIL05",
+	 * "IdeaPad Slim 7 14IIL05", "IdeaPad Slim 7 15IIL05",
+	 * "Lenovo BS145-15IIL",
+	 * "Lenovo IdeaPad S145-15IIL", "Lenovo IdeaPad S340-14IIL",
+	 * "Lenovo IdeaPad S340-15IIL", "Lenovo IdeaPad C340-15IIL",
+	 * "Lenovo V14-IIL", "Lenovo V15-IIL", "Lenovo V17-IIL",
+	 * "Lenovo Yoga S740-14IIL", "Lenovo Yoga C940-14IIL",
+	 * "Yoga Slim 7 14IIL05", "Yoga Slim 7 15IIL05"
+	 *
+	 * On some of these the bridge's _CRS method *sometimes* (under unknown
+	 * conditions) has a 64 bit [mem 0x4000000000-0x7fffffffff window].
+	 * This avoids some of the issues, but even then there are still issues
+	 * with assigning some 32 bit only BARs such as some Thunderbolt devs,
+	 * the 00:1f.5 BIOS SPI controller and BAR6 of some nvidia gfx.
+	 *
+	 * This entry also covers the following DMI_PRODUCT_VERSION-s which do
+	 * not need pci_use_e820=false. This quirk is a no-op for these models,
+	 * because there is no overlap between E820 regions and _CRS windows:
+	 * "IdeaPad Flex 5 14IIL05", "IdeaPad Flex 5 15IIL05",
+	 * "Lenovo ThinkBook 14-IIL", "Lenovo ThinkBook 15-IIL",
+	 * "Lenovo Yoga S940-14IIL"
+	 *
+	 * This entry fixes issues reported in the following bugs:
+	 * https://bugzilla.kernel.org/show_bug.cgi?id=206459
+	 * https://bugzilla.redhat.com/show_bug.cgi?id=1871793
+	 * https://bugzilla.redhat.com/show_bug.cgi?id=1868899
+	 * https://bugs.launchpad.net/bugs/1878279
+	 * https://bugs.launchpad.net/bugs/1880172
+	 * https://bugs.launchpad.net/bugs/1921649
+	 * https://bugs.launchpad.net/bugs/1931715
+	 * https://bugs.launchpad.net/bugs/1932069
+	 */
+	{
+		.callback = set_no_e820,
+		.ident = "Lenovo *IIL* product version",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_VERSION, "IIL"),
+		},
+	},
+
+	/*
+	 * The Acer Spin 5 (SP513-54N) has the same E820 reservation covering
+	 * the entire _CRS 32 bit window issue as the Lenovo *IIL* models.
+	 * https://bugs.launchpad.net/bugs/1884232
+	 */
+	{
+		.callback = set_no_e820,
+		.ident = "Acer Spin 5 (SP513-54N)",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Spin SP513-54N"),
+		},
+	},
+
 	{}
 };
 
@@ -146,6 +222,24 @@ void __init pci_acpi_crs_quirks(void)
 	if (year >= 0 && year < 2008 && iomem_resource.end <= 0xffffffff)
 		pci_use_crs = false;
 
+	/*
+	 * 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.
+	 * In 2019 some systems have shown-up with E820 reservations which cover
+	 * the entire _CRS returned PCI host bridge window, causing all attempts
+	 * to assign memory to PCI BARs to fail if Linux uses E820 reservations.
+	 *
+	 * Ideally Linux would fully stop using E820 reservations, but then
+	 * various old systems will regress. Instead stop using E820 reservations
+	 * for new systems with a DMI BIOS year >= 2023;
+	 * and use DMI quirks for existing systems on which excluding E820
+	 * reservations is known to cause issues.
+	 */
+	if (year >= 2023)
+		pci_use_e820 = false;
+
 	dmi_check_system(pci_crs_quirks);
 
 	/*
@@ -161,6 +255,15 @@ void __init pci_acpi_crs_quirks(void)
 	       "if necessary, use \"pci=%s\" and report a bug\n",
 	       pci_use_crs ? "Using" : "Ignoring",
 	       pci_use_crs ? "nocrs" : "use_crs");
+
+	/* "pci=use_e820"/"pci=no_e820" on the kernel cmdline takes precedence */
+	if (pci_probe & PCI_NO_E820)
+		pci_use_e820 = false;
+	else if (pci_probe & PCI_USE_E820)
+		pci_use_e820 = true;
+
+	printk(KERN_INFO "PCI: %s E820 reservations for host bridge windows\n",
+	       pci_use_e820 ? "Using" : "Ignoring");
 }
 
 #ifdef	CONFIG_PCI_MMCONFIG
@@ -301,8 +404,10 @@ static int pci_acpi_root_prepare_resources(struct acpi_pci_root_info *ci)
 
 	status = acpi_pci_probe_root_resources(ci);
 
-	resource_list_for_each_entry(entry, &ci->resources)
-		remove_e820_regions(&device->dev, entry->res);
+	if (pci_use_e820) {
+		resource_list_for_each_entry(entry, &ci->resources)
+			remove_e820_regions(&device->dev, entry->res);
+	}
 
 	if (pci_use_crs) {
 		resource_list_for_each_entry_safe(entry, tmp, &ci->resources)
diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 9e1e6b8d8876..ddb798603201 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -595,6 +595,14 @@ char *__init pcibios_setup(char *str)
 	} else if (!strcmp(str, "nocrs")) {
 		pci_probe |= PCI_ROOT_NO_CRS;
 		return NULL;
+	} else if (!strcmp(str, "use_e820")) {
+		pci_probe |= PCI_USE_E820;
+		add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
+		return NULL;
+	} else if (!strcmp(str, "no_e820")) {
+		pci_probe |= PCI_NO_E820;
+		add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
+		return NULL;
 #ifdef CONFIG_PHYS_ADDR_T_64BIT
 	} else if (!strcmp(str, "big_root_window")) {
 		pci_probe |= PCI_BIG_ROOT_WINDOW;
-- 
2.36.0

Re: [PATCH v8 1/1] x86/PCI: Ignore E820 reservations for bridge windows on future systems

[Rafael J. Wysocki]

On Thu, May 12, 2022 at 10:25 PM Hans de Goede <hdegoede@redhat.com> 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 future
> systems.
>
> That is ignore E820 reservations starting with systems with
> a DMI BIOS year >= 2023.
>
> And use DMI quirks for existing systems on which excluding E820
> reservations from the _CRS returned bridge window is an issue.
>
> 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/1880172
> BugLink: https://bugs.launchpad.net/bugs/1884232
> BugLink: https://bugs.launchpad.net/bugs/1921649
> BugLink: https://bugs.launchpad.net/bugs/1931715
> BugLink: https://bugs.launchpad.net/bugs/1932069
> Cc: Benoit Grégoire <benoitg@coeus.ca>
> Cc: Hui Wang <hui.wang@canonical.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
> Changes in v8:
> - Change the cut-off for no longer excluding E820 reservations from
>   the bridge window to BIOS year >= 2023 so that this only applies to
>   upcoming systems.
> - Use DMI quirks for existing systems on which excluding E820
>   reservations from the _CRS returned bridge window is an issue.
>
> Changes in v7:
> - Re-add the pci=use_e820 and pci=no_e820 kernel cmdline options since it
>   turns out that some newer laptops still need pci=use_e820
> - Add DMI quirks for known newer laptops which need pci=use_e820
>
> Changes in v6:
> - Remove the possibility to change the behavior from the commandline
>   because of worries that users may use this to paper over other problems
>
> Changes in v5:
> - Drop mention of Windows behavior from the commit msg, replace with a
>   reference to the specs
> - Improve documentation in Documentation/admin-guide/kernel-parameters.txt
> - Reword the big comment added, use "PCI host bridge window" in it and drop
>   all refences to Windows
>
> Changes in v4:
> - Rewrap the big comment block to fit in 80 columns
> - Add Rafael's Acked-by
> - Add Cc: stable@vger.kernel.org
>
> Changes in v3:
> - Commit msg tweaks (drop dmesg timestamps, typo fix)
> - Use "defined(CONFIG_...)" instead of "defined CONFIG_..."
> - Add Mika's Reviewed-by
>
> Changes in v2:
> - Replace the per model DMI quirk approach with disabling E820 reservations
>   checking for all systems with a BIOS year >= 2018
> - Add documentation for the new kernel-parameters to
>   Documentation/admin-guide/kernel-parameters.txt
> ---
>  .../admin-guide/kernel-parameters.txt         |   9 ++
>  arch/x86/include/asm/pci_x86.h                |   2 +
>  arch/x86/pci/acpi.c                           | 109 +++++++++++++++++-
>  arch/x86/pci/common.c                         |   8 ++
>  4 files changed, 126 insertions(+), 2 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
> diff --git a/arch/x86/include/asm/pci_x86.h b/arch/x86/include/asm/pci_x86.h
> index a0627dfae541..ce3fd3311772 100644
> --- a/arch/x86/include/asm/pci_x86.h
> +++ b/arch/x86/include/asm/pci_x86.h
> @@ -42,6 +42,8 @@ do {                                          \
>  #define PCI_ROOT_NO_CRS                0x100000
>  #define PCI_NOASSIGN_BARS      0x200000
>  #define PCI_BIG_ROOT_WINDOW    0x400000
> +#define PCI_USE_E820           0x800000
> +#define PCI_NO_E820            0x1000000
>
>  extern unsigned int pci_probe;
>  extern unsigned long pirq_table_addr;
> diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> index 562c81a51ea0..125c55b58d7e 100644
> --- a/arch/x86/pci/acpi.c
> +++ b/arch/x86/pci/acpi.c
> @@ -20,6 +20,7 @@ struct pci_root_info {
>  #endif
>  };
>
> +static bool pci_use_e820 = true;
>  static bool pci_use_crs = true;
>  static bool pci_ignore_seg;
>
> @@ -42,6 +43,13 @@ static int __init set_ignore_seg(const struct dmi_system_id *id)
>         return 0;
>  }
>
> +static int __init set_no_e820(const struct dmi_system_id *id)
> +{
> +       printk(KERN_INFO "PCI: %s detected: ignoring e820 regions\n", id->ident);
> +       pci_use_e820 = false;
> +       return 0;
> +}
> +
>  static const struct dmi_system_id pci_crs_quirks[] __initconst = {
>         /* http://bugzilla.kernel.org/show_bug.cgi?id=14183 */
>         {
> @@ -136,6 +144,74 @@ static const struct dmi_system_id pci_crs_quirks[] __initconst = {
>                         DMI_MATCH(DMI_PRODUCT_NAME, "HP xw9300 Workstation"),
>                 },
>         },
> +
> +       /*
> +        * Most Lenovo models with "IIL" in their DMI_PRODUCT_VERSION have
> +        * an E820 reservation which covers the entire _CRS returned 32 bit
> +        * PCI bridge memory window, causing all attempts to assign memory to
> +        * 32 bit PCI bars which have not been setup by the BIOS to fail.
> +        * Specifically this often causes some of the I2C controllers to not
> +        * work breaking touchpad support and/or this may cause issues when
> +        * hotplugging thunderbolt connected devices.
> +        *
> +        * This DMI match entry covers the following DMI_PRODUCT_VERSION-s with
> +        * an E820 reservation which covers the entire 32 bit bridge window:
> +        * "IdeaPad 3 14IIL05", "IdeaPad 3 15IIL05", "IdeaPad 3 17IIL05",
> +        * "IdeaPad 5 14IIL05", "IdeaPad 5 15IIL05",
> +        * "IdeaPad Slim 7 14IIL05", "IdeaPad Slim 7 15IIL05",
> +        * "Lenovo BS145-15IIL",
> +        * "Lenovo IdeaPad S145-15IIL", "Lenovo IdeaPad S340-14IIL",
> +        * "Lenovo IdeaPad S340-15IIL", "Lenovo IdeaPad C340-15IIL",
> +        * "Lenovo V14-IIL", "Lenovo V15-IIL", "Lenovo V17-IIL",
> +        * "Lenovo Yoga S740-14IIL", "Lenovo Yoga C940-14IIL",
> +        * "Yoga Slim 7 14IIL05", "Yoga Slim 7 15IIL05"
> +        *
> +        * On some of these the bridge's _CRS method *sometimes* (under unknown
> +        * conditions) has a 64 bit [mem 0x4000000000-0x7fffffffff window].
> +        * This avoids some of the issues, but even then there are still issues
> +        * with assigning some 32 bit only BARs such as some Thunderbolt devs,
> +        * the 00:1f.5 BIOS SPI controller and BAR6 of some nvidia gfx.
> +        *
> +        * This entry also covers the following DMI_PRODUCT_VERSION-s which do
> +        * not need pci_use_e820=false. This quirk is a no-op for these models,
> +        * because there is no overlap between E820 regions and _CRS windows:
> +        * "IdeaPad Flex 5 14IIL05", "IdeaPad Flex 5 15IIL05",
> +        * "Lenovo ThinkBook 14-IIL", "Lenovo ThinkBook 15-IIL",
> +        * "Lenovo Yoga S940-14IIL"
> +        *
> +        * This entry fixes issues reported in the following bugs:
> +        * https://bugzilla.kernel.org/show_bug.cgi?id=206459
> +        * https://bugzilla.redhat.com/show_bug.cgi?id=1871793
> +        * https://bugzilla.redhat.com/show_bug.cgi?id=1868899
> +        * https://bugs.launchpad.net/bugs/1878279
> +        * https://bugs.launchpad.net/bugs/1880172
> +        * https://bugs.launchpad.net/bugs/1921649
> +        * https://bugs.launchpad.net/bugs/1931715
> +        * https://bugs.launchpad.net/bugs/1932069
> +        */
> +       {
> +               .callback = set_no_e820,
> +               .ident = "Lenovo *IIL* product version",
> +               .matches = {
> +                       DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
> +                       DMI_MATCH(DMI_PRODUCT_VERSION, "IIL"),
> +               },
> +       },
> +
> +       /*
> +        * The Acer Spin 5 (SP513-54N) has the same E820 reservation covering
> +        * the entire _CRS 32 bit window issue as the Lenovo *IIL* models.
> +        * https://bugs.launchpad.net/bugs/1884232
> +        */
> +       {
> +               .callback = set_no_e820,
> +               .ident = "Acer Spin 5 (SP513-54N)",
> +               .matches = {
> +                       DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
> +                       DMI_MATCH(DMI_PRODUCT_NAME, "Spin SP513-54N"),
> +               },
> +       },
> +
>         {}
>  };
>
> @@ -146,6 +222,24 @@ void __init pci_acpi_crs_quirks(void)
>         if (year >= 0 && year < 2008 && iomem_resource.end <= 0xffffffff)
>                 pci_use_crs = false;
>
> +       /*
> +        * 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.
> +        * In 2019 some systems have shown-up with E820 reservations which cover
> +        * the entire _CRS returned PCI host bridge window, causing all attempts
> +        * to assign memory to PCI BARs to fail if Linux uses E820 reservations.
> +        *
> +        * Ideally Linux would fully stop using E820 reservations, but then
> +        * various old systems will regress. Instead stop using E820 reservations
> +        * for new systems with a DMI BIOS year >= 2023;
> +        * and use DMI quirks for existing systems on which excluding E820
> +        * reservations is known to cause issues.
> +        */
> +       if (year >= 2023)
> +               pci_use_e820 = false;
> +
>         dmi_check_system(pci_crs_quirks);
>
>         /*
> @@ -161,6 +255,15 @@ void __init pci_acpi_crs_quirks(void)
>                "if necessary, use \"pci=%s\" and report a bug\n",
>                pci_use_crs ? "Using" : "Ignoring",
>                pci_use_crs ? "nocrs" : "use_crs");
> +
> +       /* "pci=use_e820"/"pci=no_e820" on the kernel cmdline takes precedence */
> +       if (pci_probe & PCI_NO_E820)
> +               pci_use_e820 = false;
> +       else if (pci_probe & PCI_USE_E820)
> +               pci_use_e820 = true;
> +
> +       printk(KERN_INFO "PCI: %s E820 reservations for host bridge windows\n",
> +              pci_use_e820 ? "Using" : "Ignoring");
>  }
>
>  #ifdef CONFIG_PCI_MMCONFIG
> @@ -301,8 +404,10 @@ static int pci_acpi_root_prepare_resources(struct acpi_pci_root_info *ci)
>
>         status = acpi_pci_probe_root_resources(ci);
>
> -       resource_list_for_each_entry(entry, &ci->resources)
> -               remove_e820_regions(&device->dev, entry->res);
> +       if (pci_use_e820) {
> +               resource_list_for_each_entry(entry, &ci->resources)
> +                       remove_e820_regions(&device->dev, entry->res);
> +       }
>
>         if (pci_use_crs) {
>                 resource_list_for_each_entry_safe(entry, tmp, &ci->resources)
> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> index 9e1e6b8d8876..ddb798603201 100644
> --- a/arch/x86/pci/common.c
> +++ b/arch/x86/pci/common.c
> @@ -595,6 +595,14 @@ char *__init pcibios_setup(char *str)
>         } else if (!strcmp(str, "nocrs")) {
>                 pci_probe |= PCI_ROOT_NO_CRS;
>                 return NULL;
> +       } else if (!strcmp(str, "use_e820")) {
> +               pci_probe |= PCI_USE_E820;
> +               add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
> +               return NULL;
> +       } else if (!strcmp(str, "no_e820")) {
> +               pci_probe |= PCI_NO_E820;
> +               add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
> +               return NULL;
>  #ifdef CONFIG_PHYS_ADDR_T_64BIT
>         } else if (!strcmp(str, "big_root_window")) {
>                 pci_probe |= PCI_BIG_ROOT_WINDOW;
> --
> 2.36.0
>