x86/pci: Comment pci_mmconfig_insert() obscure MCFG dependency

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In pci_mmconfig_insert(), there's no reference to "addr" between locking
pci_mmcfg_lock and testing "addr", so it *looks* like we should move the
test before the lock.

But 07f9b61c39 ("x86/PCI: MMCONFIG: Check earlier for MMCONFIG region at
address zero") did that, which broke things by returning -EINVAL when
"addr" is zero instead of -EEXIST.

So 07f9b61c39 was reverted by 67d470e0e1 ("Revert "x86/PCI: MMCONFIG:
Check earlier for MMCONFIG region at address zero"").

Add a comment about this issue to prevent it from happening again.

Link: https://lore.kernel.org/r/20231121183643.249006-8-helgaas@kernel.org
Tested-by: Tomasz Pala <gotar@polanet.pl>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

...

This commit is contained in:

Bjorn Helgaas 2023-11-21 12:36:41 -06:00

parent d26e7fc3d9

commit f284dff47b

1 changed files with 4 additions and 0 deletions

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arch/x86/pci/mmconfig-shared.c

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