----- On Nov 20, 2017, at 1:03 PM, Thomas Gleixner tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org wrote:

On Mon, 20 Nov 2017, Thomas Gleixner wrote:

quoted

On Mon, 20 Nov 2017, Mathieu Desnoyers wrote:

quoted

quoted

quoted

+ * The reason why we require all pointer offsets to be calculated by
+ * user-space beforehand is because we need to use get_user_pages_fast()
+ * to first pin all pages touched by each operation. This takes care of

That doesnt explain it either.

What kind of explication are you looking for here ? Perhaps being too close
to the implementation prevents me from understanding what is unclear from
your perspective.

What the heck are pointer offsets?

The ops have one or two pointer(s) to a lump of memory. So if a pointer
points to the wrong lump of memory then you're screwed, but that's true for
all pointers handed to the kernel.

So I think you mix here the 'user space programmer guide - how to set up
the magic ops - into the kernel side documentation. The kernel side does
not care about the pointers, as long as they are valid to access.

Again. Try to explain things at the conceptual level.

Yes, I took the sentence you suggested for that reason: it removes
usage details that are meant for user-space implementer, which do not
belong in those comments.

Thanks,

Mathieu

Thanks,

	tglx

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com