Re: Replacement for page fault notifiers?

Benjamin Herrenschmidt
2008-01-09T19:59:19Z

On Wed, 2008-01-09 at 18:21 +0000, Christoph Hellwig wrote:
> On Wed, Jan 09, 2008 at 01:18:44PM -0500, Pavel Roskin wrote:
> > notification without patching the kernel. But if no such solution is
> > found, I would also support reverting the patch that removed fault
> > notifiers on i386.
>
> With your fixation on not patching the kernel you sound like a windows
> developer. There is no problem with patching the kernel, but the best
> patching of that kernel is that which happens upstream so please folks
> start submitting an mmiotrace variant for kernel inclusion.
>
> Then again I don't quite get why you absolutely want to track pagefaults
> anyway. Just hooking into ioremap and read*/write* and iomap +
> ioread*/iowrite* would be much easier and also a lot faster. It would
> also allow adding a nice sysfs attribute to enable this per-device.

Because binary drivers don't use ioread/iowrite/readX/writeX (or if they
do, they've long been inlined in the blob). The only solution is to map
things as non-accessible and trap the page faults.

It's a sane thing to do, Christoph, I don't think it's a unreasonable
request to put the hooks back in.

Cheers,
Ben.