Messages in this thread |  | | | Date | Mon, 24 Dec 2007 11:13:55 -0600 | | From | Robert Hancock <> | | Subject | Re: [Fwd: Re: [PATCH 0/5]PCI: x86 MMCONFIG] |
| |
Loic Prylli wrote: > I just realized one thing: the bar sizing code in pci_read_bases() (that > writes 0xffffffff in the bars) does not seem to disable the > PCI_COMMAND_MEM/PCI_COMMAND_IO bits in the cmd register before > manipulating the BARs. And it seems nobody else ensures they are > disabled at this point either (or am I missing something?).
No you're not missing anything. This problem causes many machines to break horribly when MMCONFIG is enabled. There's a patch in -mm to fix this. (It special-cases the case of host bridges and doesn't disable the decode bits for those, since some are known to do crazy things if you do that.)
http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.24-rc6/2.6.24-rc6-mm1/broken-out/pci-disable-decoding-during-sizing-of-bars.patch
> > Touching the bars while they are enabled would be buggy behaviour from > our part, and something trivial to fix. And it might well fix that > particular problem (it's fair play from the machine to crash if we > create a decoding conflict, simply disabling the cmd bits in > pci_read_bases() should remove that conflict). > > FWIW, to partially answer your last question, Windows does disable > mem-space and/or IO-space when sizing the bars of a device (I have some > traces of configuration-space-access taken on a window machine for one > of the PCI busses).
Good to know. There was some speculation that it did not.
-- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/
|  |