linux-kernel - RESEND: MMCONFIG related question

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Date:   Fri, 13 Jan 2023 10:15:45 +0000
From:   "Duan, Zhenzhong" <zhenzhong.duan@...el.com>
To:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yang, Lixiao" <lixiao.yang@...el.com>,
        "Peng, Chao P" <chao.p.peng@...el.com>
Subject: RESEND: MMCONFIG related question

(Resend due to format issue)

Hi Helgaas,

Recently Lixiao reported sriov disappered for cards which supported sriov. We found it's related to commit "07eab0901ed efi/x86: Remove EfiMemoryMappedIO from E820 map" which removed EfiMemoryMappedIO regions from E820 map which lead to pci_mmcfg_reject_broken() check failed, raw_pci_ext_ops isn't set to pci_mmcfg finally, below is the related log. I know maybe bios should add MMCONFIG region into ACPI motherboard resources, just want to ask if we would support the case when MMCONFIG is missed in ACPI motherboard resources as I see it's treated as "Firmware Info" not "Firmware bug". Thanks

Also has another question, if MMCONFIG happened to be in EfiMemoryMappedIO, even if it's removed from E820 map so that there is no CRS clip for that region, could it be used for BAR space? Will there be conflict for BAR and MMCONFIG access?

[    0.000000] efi: EFI v2.60 by EDK II BIOS ID:SE5C620.86B.01.00.0763.022420181017
[    0.000000] efi: SMBIOS=0x6ae78000 ACPI=0x6bbab000 ACPI 2.0=0x6bbab014 MEMATTR=0x67e99018 MOKvar=0x67b2d000
[    0.000000] efi: Not removing mem06: MMIO range=[0xfe000000-0xfe010fff] (68KB) from e820 map
[    0.000000] efi: Remove mem09: MMIO range=[0x80000000-0x8fffffff] (256MB) from e820 map
[    0.000000] e820: remove [mem 0x80000000-0x8fffffff] reserved
[    3.351098] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000)
[    3.351742] PCI: not using MMCONFIG
[    4.867853] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000)
[    4.904325] [Firmware Info]: PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] not reserved in ACPI motherboard resources
[    4.905061] PCI: not using MMCONFIG

Regards
Zhenzhong