Re: [PATCH 1/1] x86/pci: Skip early E820 check for ECAM region

[Kuppuswamy Sathyanarayanan]

On 4/17/24 1:40 PM, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> Arul, Mateusz, Imcarneiro91, and Aman reported a regression caused by
> 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map").  On the
> Lenovo Legion 9i laptop, that commit removes the area containing ECAM from
> E820, which means the early E820 validation started failing, which meant we
> didn't enable ECAM in the "early MCFG" path
>
> The lack of ECAM caused many ACPI methods to fail, resulting in the
> embedded controller, PS/2, audio, trackpad, and battery devices not being
> detected.  The _OSC method also failed, so Linux could not take control of
> the PCIe hotplug, PME, and AER features:
>
>   # pci_mmcfg_early_init()
>
>   PCI: ECAM [mem 0xc0000000-0xce0fffff] (base 0xc0000000) for domain 0000 [bus 00-e0]
>   PCI: not using ECAM ([mem 0xc0000000-0xce0fffff] not reserved)
>
>   ACPI Error: AE_ERROR, Returned by Handler for [PCI_Config] (20230628/evregion-300)
>   ACPI: Interpreter enabled
>   ACPI: Ignoring error and continuing table load
>   ACPI BIOS Error (bug): Could not resolve symbol [\_SB.PC00.RP01._SB.PC00], AE_NOT_FOUND (20230628/dswload2-162)
>   ACPI Error: AE_NOT_FOUND, During name lookup/catalog (20230628/psobject-220)
>   ACPI: Skipping parse of AML opcode: OpcodeName unavailable (0x0010)
>   ACPI BIOS Error (bug): Could not resolve symbol [\_SB.PC00.RP01._SB.PC00], AE_NOT_FOUND (20230628/dswload2-162)
>   ACPI Error: AE_NOT_FOUND, During name lookup/catalog (20230628/psobject-220)
>   ...
>   ACPI Error: Aborting method \_SB.PC00._OSC due to previous error (AE_NOT_FOUND) (20230628/psparse-529)
>   acpi PNP0A08:00: _OSC: platform retains control of PCIe features (AE_NOT_FOUND)
>
>   # pci_mmcfg_late_init()
>
>   PCI: ECAM [mem 0xc0000000-0xce0fffff] (base 0xc0000000) for domain 0000 [bus 00-e0]
>   PCI: [Firmware Info]: ECAM [mem 0xc0000000-0xce0fffff] not reserved in ACPI motherboard resources
>   PCI: ECAM [mem 0xc0000000-0xce0fffff] is EfiMemoryMappedIO; assuming valid
>   PCI: ECAM [mem 0xc0000000-0xce0fffff] reserved to work around lack of ACPI motherboard _CRS
>
> Per PCI Firmware r3.3, sec 4.1.2, ECAM space must be reserved by a PNP0C02
> resource, but it need not be mentioned in E820, so we shouldn't look at
> E820 to validate the ECAM space described by MCFG.
>
> 946f2ee5c731 ("[PATCH] i386/x86-64: Check that MCFG points to an e820
> reserved area") added a sanity check of E820 to work around buggy MCFG
> tables, but that over-aggressive validation causes failures like this one.
>
> Keep the E820 validation check only for older BIOSes (pre-2016) so the
> buggy 2006-era machines don't break.  Skip the early E820 check for 2016
> and newer BIOSes.
>
> Fixes: 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map")
> Reported-by: Mateusz Kaduk <mateusz.kaduk@xxxxxxxxx>
> Reported-by: Arul <...>
> Reported-by: Imcarneiro91 <...>
> Reported-by: Aman <...>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218444
> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Tested-by: Mateusz Kaduk <mateusz.kaduk@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---

LGTM

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

>  arch/x86/pci/mmconfig-shared.c | 35 +++++++++++++++++++++++++++-------
>  1 file changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
> index 0cc9520666ef..53c7afa606c3 100644
> --- a/arch/x86/pci/mmconfig-shared.c
> +++ b/arch/x86/pci/mmconfig-shared.c
> @@ -518,7 +518,34 @@ static bool __ref pci_mmcfg_reserved(struct device *dev,
>  {
>  	struct resource *conflict;
>  
> -	if (!early && !acpi_disabled) {
> +	if (early) {
> +
> +		/*
> +		 * Don't try to do this check unless configuration type 1
> +		 * is available.  How about type 2?

I don't understand why above question is included in the comment. Do
you think it is better to drop that part of the comment?

> +		 */
> +
> +		/*
> +		 * 946f2ee5c731 ("Check that MCFG points to an e820
> +		 * reserved area") added this E820 check in 2006 to work
> +		 * around BIOS defects.
> +		 *
> +		 * Per PCI Firmware r3.3, sec 4.1.2, ECAM space must be
> +		 * reserved by a PNP0C02 resource, but it need not be
> +		 * mentioned in E820.  Before the ACPI interpreter is
> +		 * available, we can't check for PNP0C02 resources, so
> +		 * there's no reliable way to verify the region in this
> +		 * early check.  Keep it only for the old machines that
> +		 * motivated 946f2ee5c731.
> +		 */
> +		if (dmi_get_bios_year() < 2016 && raw_pci_ops)
> +			return is_mmconf_reserved(e820__mapped_all, cfg, dev,
> +						  "E820 entry");
> +
> +		return true;
> +	}
> +
> +	if (!acpi_disabled) {
>  		if (is_mmconf_reserved(is_acpi_reserved, cfg, dev,
>  				       "ACPI motherboard resource"))
>  			return true;
> @@ -554,12 +581,6 @@ static bool __ref pci_mmcfg_reserved(struct device *dev,
>  	if (pci_mmcfg_running_state)
>  		return true;
>  
> -	/* Don't try to do this check unless configuration
> -	   type 1 is available. how about type 2 ?*/
> -	if (raw_pci_ops)
> -		return is_mmconf_reserved(e820__mapped_all, cfg, dev,
> -					  "E820 entry");
> -
>  	return false;
>  }
>  

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer