EDAC on arm64

[Catalin Marinas]

On Mon, Mar 02, 2015 at 10:34:16AM -0600, Rob Herring wrote:
> On Mon, Mar 2, 2015 at 8:58 AM, Catalin Marinas <catalin.marinas at arm.com> wrote:
> > On Mon, Mar 02, 2015 at 10:59:32AM +0000, Will Deacon wrote:
> >> On Sat, Feb 28, 2015 at 12:52:03AM +0000, Jon Masters wrote:
> >> > Have you considered reviving the patch you posted previously for EDAC
> >> > support (the atomic_scrub read/write test piece dependency)?
> >> >
> >> > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-April/249039.html
> >>
> >> Well, we'd need a way to handle the non-coherent DMA case and it's really
> >> not clear how to fix that.
> >
> > I agree, that's where the discussions stopped. Basically the EDAC memory
> > writing is racy with any non-cacheable memory accesses (by CPU or
> > device). The only way we could safely use this is only if all the
> > devices are coherent *and* KVM is disabled. With KVM, guests may access
> > the memory uncached, so we hit the same problem.
> 
> Scrubbing only prevents repeated error reporting of correctable errors
> which only repeat on a cache miss. Perhaps we should just add an empty
> version that is a nop. At least then we can enable EDAC and be able to
> report errors. Otherwise, they may just be silently ignored (fine for
> correctable, but not so good to do with uncorrectable errors).

This looks fine to me.

> Anyway, I'll leave it to someone who still has this itch to sort out.

Maybe Jon? ;)

-- 
Catalin