Messages in this thread | | | Date | Wed, 14 Jun 2006 17:07:26 -0400 | From | Brice Goglin <> | Subject | [RFC] PCI extended conf space when MMCONFIG disabled because of e820 |
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Hi Arjan,
We have some machines here where MMCONFIG is disabled in 2.6.17 because their MCFG area is not e820-reserved. It makes the extended PCI config space unavailable to pci_read/write_config_foo(). I don't know if lots of people out there use the extended config space, but at least we do in our myri10ge driver.
What would you think of a patch implementing the following strategy: 1) if MMCONFIG works, always use it (no change) 2) if MMCONFIG is disabled and we are accessing the regular config space, use direct conf (no change, should ensure that any machine will still boot fine) 3) if MMCONFIG is disabled but we are accessing the _extended_ config space, try mmconfig anyway since there's no other way to do it.
Actually, this problem seems to target nVidia chipsets, and we actually know how to check this chipset's registers to be sure whether MMCONFIG works. So it might be good to improve the current MMCONFIG disabling code by adding some chipset-specific hacks (having nVidia and Intel chipsets there may cover most of the cases). I don't think there's any way to do that with PCI quirks. We might end up having these hacks in the MMCONFIG initialization code.
Thanks, Brice
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