Re: [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks

[Bjorn Helgaas]

On Wed, Nov 18, 2020 at 07:36:08PM -0300, Guilherme Piccoli wrote:
> Thanks a lot Bjorn! I confess except for PPC64 Server machines, I
> never saw other "domains" or segments. Is it common in x86 to have
> that? The early_quirks() are restricted to the first segment, no
> matter how many host bridges we have in segment 0000?

I don't know whether it's *common* to have multiple domains on x86,
but they're definitely used on large systems.  This includes some
lspci info from an HPE Superdome Flex system:
https://lore.kernel.org/lkml/5350E02A-6457-41A8-8F33-AF67BFDAEE3E@xxxxxx/

The early quirks in arch/x86/kernel/early-quirks.c (not the
DECLARE_PCI_FIXUP_EARLY quirks in drivers/pci/quirks.c) are restricted
to segment 0, no matter how many host bridges there are.  This is
because they use read_pci_config_16(), which uses a config access
mechanism that has no provision for a segment number.

Bjorn