On 05.01.17 12:08:20, Will Deacon wrote:

On Thu, Jan 05, 2017 at 12:24:07PM +0100, Robert Richter wrote:

quoted

On 04.01.17 14:02:23, Will Deacon wrote:

quoted

Using early_pfn_valid feels like a bodge to me, since having pfn_valid
return false for something that early_pfn_valid says is valid (and is
therefore initialised in the memmap) makes the NOMAP semantics even more
confusing.

The concern I have had with HOLES_IN_ZONE is that it enables
pfn_valid_within() for arm64. This means that each pfn of a section is
checked which is done only once for the section otherwise. With up to
2^18 pages per section we traverse the memblock list by that factor
more often. There could be a performance regression.

There could be, but we're trying to fix a bug here. I wouldn't have
thought that walking over pfns like that is done very often.

The bug happens on a small number of machines depending on the memory
layout. The fix affects all systems. And right know the impact is
unclear.

quoted

I haven't numbers yet, since the fix causes another kernel crash. And,
this is the next problem I have. The crash doesn't happen otherwise. So,
either it uncovers another bug or the fix is incomplete. Though the
changes look like it should work. This needs more investigation.

I really can't see how the fix causes a crash, and I couldn't reproduce
it on any of my boards, nor could any of the Linaro folk afaik. Are you
definitely running mainline with just these two patches from Ard?

Yes, just both patches applied. Various other solutions were working.

-Robert