Re: [PATCH 2/2] x86/pci: Treat EfiMemoryMappedIO as reservation of ECAM space

[Bjorn Helgaas]

On Thu, Oct 12, 2023 at 05:33:47PM +0200, Tomasz Pala wrote:
> On Tue, Jan 10, 2023 at 12:02:43 -0600, Bjorn Helgaas wrote:
> 
> > Normally we reject ECAM space unless it is reported as reserved in the E820
> > table or via a PNP0C02 _CRS method (PCI Firmware, r3.3, sec 4.1.2).  This
> > means PCI extended config space (offsets 0x100-0xfff) may not be accessible.
> > 
> > Some firmware doesn't report ECAM space via PNP0C02 _CRS methods, but does
> > mention it as an EfiMemoryMappedIO region via EFI GetMemoryMap(), which is
> > normally converted to an E820 entry by a bootloader or EFI stub.
> > 
> > 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map"), removes
> > E820 entries that correspond to EfiMemoryMappedIO regions because some
> > other firmware uses EfiMemoryMappedIO for PCI host bridge windows, and the
> > E820 entries prevent Linux from allocating BAR space for hot-added devices.
> > 
> > Allow use of ECAM for extended config space when the region is covered by
> > an EfiMemoryMappedIO region, even if it's not included in E820 or PNP0C02
> > _CRS.
> 
> I'm still having a problem initializing ixgbe NICs with pristine 6.5.7 kernel.
> 
> efi: Remove mem63: MMIO range=[0x80000000-0x8fffffff] (256MB) from e820 map
> [...]
> [mem 0x7f800000-0xfed1bfff] available for PCI devices
> [...]
> PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000)
> [Firmware Info]: PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] not reserved in ACPI motherboard resources
> PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] reserved as EfiMemoryMappedIO
> [...]
> ixgbe 0000:02:00.0: enabling device (0140 -> 0142)
> ixgbe 0000:02:00.0: BAR 0: can't reserve [mem 0x80000000-0x8007ffff 64bit]
> ixgbe 0000:02:00.0: pci_request_selected_regions failed 0xfffffff0
> ixgbe: probe of 0000:02:00.0 failed with error -16
> 
> 
> After disabling the code causing this (using always-false condition:
> 		if (size >= 256*1024 && 0) {
> ) in the chunk:
> 
> https://lore.kernel.org/lkml/20221208190341.1560157-2-helgaas@xxxxxxxxxx/
> 
> the BAR starts at 0x90000000 (not 0x80000000):
> 
> efi: Not removing mem63: MMIO range=[0x80000000-0x8fffffff] (262144KB) from e820 map
> [...]
> [mem 0x90000000-0xfed1bfff] available for PCI devices
> [...]
> PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0x80000000-0x8fffffff] (base 0x80000000)
> PCI: MMCONFIG at [mem 0x80000000-0x8fffffff] reserved as E820 entry
> 
> and everything seems to work again.

Adding to regression tracking:

#regzbot ^introduced: 07eab0901ede ("efi/x86: Remove EfiMemoryMappedIO from E820 map")
#regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=218107