Messages in this thread | | | Date | Mon, 20 Nov 2017 18:42:00 +0000 (UTC) | From | Mathieu Desnoyers <> | Subject | Re: [RFC PATCH v3 for 4.15 08/24] Provide cpu_opv system call |
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----- On Nov 20, 2017, at 1:03 PM, Thomas Gleixner tglx@linutronix.de 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
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