Ingo Molnar wrote:
* H. Peter Anvin <[email protected]> wrote:
Pavel Machek wrote:
this is also something for v2.6.24 merging.
As much as I like this patch, I do not think it is suitable for
.24. Too risky, I'd say.
No kidding! We're talking about removing a hack that has been
successful on thousands of pieces of hardware over 15 years because it
^----[*]
breaks ONE machine.
[*] "- none of which needs it anymore -"
there, fixed it for you ;-)
So lets keep this in perspective: this is a hack that only helps on a
very low number of systems. (the PIT of one PII era chipset is known to
be affected)
unfortunately this hack's side-effects are mis-used by an unknown number
of drivers to mask PCI posting bugs. We want to figure out those bugs
(safely and carefully) and we want to remove this hack from modern
machines that dont need it. Doing anything else would be superstition.
Are there any such examples known of such drivers? It doesn't seem to
make much sense.. PCI IO writes are not posted on any known system (the
spec allows them to be posted in the host bus bridge, but if they were
they could only be flushed by a read, not a write) and PCI MMIO writes
are only guaranteed to flush by doing a read from that device, not by
other random port accesses. I suppose using the _p versions of port
accesses might happen to mask such problems on certain machines..
--
Robert Hancock Saskatoon, SK, Canada
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Home Page: http://www.roberthancock.com/
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