----- On Nov 20, 2017, at 1:03 PM, Thomas Gleixner tglx@xxxxxxxxxxxxx wrote: > On Mon, 20 Nov 2017, Thomas Gleixner wrote: >> On Mon, 20 Nov 2017, Mathieu Desnoyers wrote: >> > >> + * 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 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
