Jesse Barnes wrote:
On Wednesday, May 23, 2007 4:04 pm David Miller wrote:
From: Linus Torvalds <[email protected]>
Date: Wed, 23 May 2007 15:16:23 -0700 (PDT)
That crap should be seen for the crap it is! Dammit, how hard can
it be to just admit that mmconfig isn't that great?
I knew mmconfig was broken conceptually the first time I started
seeing write posting "bug fixes" for it that would do a read back
from PCI config space via mmconfig to post the write, which of course
has potential side-effects on the device and is absolutely illegal if
the write just performed put the device into a PM state or whatever.
I've actually seen that specific form of posted write flushing cause
crashes on some machines, so yes, it sucks.
Unfortunately, I don't think we have any other way of getting at
extended config space on x86, unless EFI provides methods or something,
but I'm not sure that would be an improvement...
That "fix" shouldn't be needed at all, the MMCONFIG memory range
shouldn't be covered by PCI ordering rules, so there should be no such
thing as write posting. I suspect that the author of such patch(es) was
doing so out of some misguided sense that it was needed. (And if there
is some chipset where it is actually needed, better just disable
MMCONFIG on that one, as there's no way to use it sanely.)
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from [email protected]
Home Page: http://www.roberthancock.com/
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