Re: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all pages returned

[Alan Stern]

On Fri, 30 Jan 2015, Andi Kleen wrote:

> > We don't "need" any backward compatility, why not fix the broken drivers
> > that are using memory outside of what they are asking for?  That's not
> > ok no matter what, right?
> 
> How would you find them all?
> 
> We don't even know which place in XHCI is the culprit here.

It shouldn't be too hard to find, expecially if the fault can easily 
be reproduced.

There are only about half a dozen calls to dma_alloc_coherent in the
xhci-hcd driver.  Just add 64 KB to the requested memory size in each
of them.  Then one-by-one (or using bisection) remove the extra size
and see which spots trigger the fault.

Alan Stern

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