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SubjectRe: [PATCH v3] x86/PCI: Ignore E820 reservations for bridge windows on newer systems
On Thu, Oct 14, 2021 at 1:04 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Some BIOS-es contain a bug where they add addresses which map to system RAM
> in the PCI bridge memory window returned by the ACPI _CRS method, see
> commit 4dc2287c1805 ("x86: avoid E820 regions when allocating address
> space").
>
> To avoid this Linux by default excludes E820 reservations when allocating
> addresses since 2010. Windows however ignores E820 reserved regions for PCI
> mem allocations, so in hindsight Linux honoring them is a problem.
>
> Recently (2020) 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]
>
> Ideally Linux would fully stop honoring E820 reservations for PCI mem
> allocations, but then the old systems this was added for will regress.
> Instead keep the old behavior for old systems, while ignoring the E820
> reservations like Windows does 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, while at the same time also taking into account that the
> systems for which the E820 checking was originally added may have
> received BIOS updates for quite a while (esp. CVE related ones),
> giving them a more recent BIOS year then 2010.
>
> Also add pci=no_e820 and pci=use_e820 options to allow overriding
> the BIOS year heuristic.
>
> 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>
> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

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

with one tiny nit below.

Or please let me know if you want me to pick this up.

> ---
> 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
> ---
> Other patches trying to address the same issue:
> https://lore.kernel.org/r/20210624095324.34906-1-hui.wang@canonical.com
> https://lore.kernel.org/r/20200617164734.84845-1-mika.westerberg@linux.intel.com
> V1 patch:
> https://lore.kernel.org/r/20211005150956.303707-1-hdegoede@redhat.com
> ---
> .../admin-guide/kernel-parameters.txt | 6 ++++
> arch/x86/include/asm/pci_x86.h | 10 +++++++
> arch/x86/kernel/resource.c | 4 +++
> arch/x86/pci/acpi.c | 29 +++++++++++++++++++
> arch/x86/pci/common.c | 6 ++++
> 5 files changed, 55 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 43dc35fe5bc0..969cde5d74c8 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3949,6 +3949,12 @@
> 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] Honor E820 reservations when allocating
> + PCI host bridge memory. If you need to use this,
> + please report a bug.
> + no_e820 [X86] ignore E820 reservations when allocating
> + PCI host bridge memory. If you need to use this,
> + please report a bug.
> 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 490411dba438..0bb4e7dd0ffc 100644
> --- a/arch/x86/include/asm/pci_x86.h
> +++ b/arch/x86/include/asm/pci_x86.h
> @@ -39,6 +39,8 @@ 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;
> @@ -64,6 +66,8 @@ void pcibios_scan_specific_bus(int busn);
>
> /* pci-irq.c */
>
> +struct pci_dev;
> +
> struct irq_info {
> u8 bus, devfn; /* Bus, device and function */
> struct {
> @@ -232,3 +236,9 @@ static inline void mmio_config_writel(void __iomem *pos, u32 val)
> # define x86_default_pci_init_irq NULL
> # define x86_default_pci_fixup_irqs NULL
> #endif
> +
> +#if defined(CONFIG_PCI) && defined(CONFIG_ACPI)
> +extern bool pci_use_e820;
> +#else
> +#define pci_use_e820 false
> +#endif
> diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c
> index 9b9fb7882c20..e8dc9bc327bd 100644
> --- a/arch/x86/kernel/resource.c
> +++ b/arch/x86/kernel/resource.c
> @@ -1,6 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0
> #include <linux/ioport.h>
> #include <asm/e820/api.h>
> +#include <asm/pci_x86.h>
>
> static void resource_clip(struct resource *res, resource_size_t start,
> resource_size_t end)
> @@ -28,6 +29,9 @@ static void remove_e820_regions(struct resource *avail)
> int i;
> struct e820_entry *entry;
>
> + if (!pci_use_e820)
> + return;
> +
> for (i = 0; i < e820_table->nr_entries; i++) {
> entry = &e820_table->entries[i];
>
> diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> index 948656069cdd..6c2febe84b6f 100644
> --- a/arch/x86/pci/acpi.c
> +++ b/arch/x86/pci/acpi.c
> @@ -21,6 +21,8 @@ struct pci_root_info {
>
> static bool pci_use_crs = true;
> static bool pci_ignore_seg = false;
> +/* Consumed in arch/x86/kernel/resource.c */
> +bool pci_use_e820 = false;
>
> static int __init set_use_crs(const struct dmi_system_id *id)
> {
> @@ -160,6 +162,33 @@ 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");
> +
> + /*
> + * Some BIOS-es contain a bug where they add addresses which map to system
> + * RAM in the PCI bridge memory window returned by the ACPI _CRS method, see
> + * commit 4dc2287c1805 ("x86: avoid E820 regions when allocating address space").
> + * To avoid this Linux by default excludes E820 reservations when allocating
> + * addresses since 2010. Windows however ignores E820 reserved regions for
> + * PCI mem allocations, so in hindsight Linux honoring them is a problem.
> + * In 2020 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 to fail if Linux honors the E820 reservations.
> + *
> + * Ideally Linux would fully stop honoring E820 reservations for PCI mem
> + * allocations, but then the old systems this was added for will regress.
> + * Instead keep the old behavior for old systems, while ignoring the E820
> + * reservations like Windows does for any systems from now on.
> + */
> + if (year >= 0 && year < 2018)
> + pci_use_e820 = true;
> +
> + 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 ? "Honoring" : "Ignoring");

Why not pr_info()?

> }
>
> #ifdef CONFIG_PCI_MMCONFIG
> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> index 3507f456fcd0..091ec7e94fcb 100644
> --- a/arch/x86/pci/common.c
> +++ b/arch/x86/pci/common.c
> @@ -595,6 +595,12 @@ 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;
> + return NULL;
> + } else if (!strcmp(str, "no_e820")) {
> + pci_probe |= PCI_NO_E820;
> + return NULL;
> #ifdef CONFIG_PHYS_ADDR_T_64BIT
> } else if (!strcmp(str, "big_root_window")) {
> pci_probe |= PCI_BIG_ROOT_WINDOW;
> --

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