Re: [patch 0/4] x86: PAT followup - Incremental changes and bugfixes

[Ingo Molnar]

* Andreas Herrmann3 <andreas.herrmann3@xxxxxxx> wrote:

> On Thu, Jan 17, 2008 at 10:42:09PM +0100, Ingo Molnar wrote:
> > 
> > * Siddha, Suresh B <suresh.b.siddha@xxxxxxxxx> wrote:
> > 
> > > On Thu, Jan 17, 2008 at 10:13:08PM +0100, Ingo Molnar wrote:
> > > > but in general we must be robust enough in this case and just degrade 
> > > > any overlapping page to UC (and emit a warning perhaps) - instead of 
> > > > failing the ioremap and thus failing the driver (and the bootup).
> > > 
> > > But then, this will cause an attribute conflicit. Old one was 
> > > specifying WB in PAT (ioremap with noflags) and the new ioremap 
> > > specifies UC.
> > 
> > we could fix up all aliases of that page as well and degrade them to UC?
> 
> Yes, we must fix all aliases or reject the conflicting mapping. But 
> fixing all aliases might not be that easy. (I've just seen a panic 
> when using your patch ;-(

yes, indeed my patch is bad if you have PAT enabled: conflicting cache 
attributes might be present. I'll go with your patch for now.

should we perhaps do UC by default for early_ioremap() as well? Normally 
those mappings are only temporary - but in case of a leak they might 
hang around in the pagetables and the CPU might stumble upon them. Also, 
should early_iounmap() do a wbinvd() [/clflush()] call as well, to be 
safe?

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/