On Thu, Jan 12, 2012 at 9:11 PM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Thu, Jan 12, 2012 at 08:04:43PM +0000, Russell King - ARM Linux wrote: >> On Thu, Jan 12, 2012 at 10:42:57AM -0800, Tony Lindgren wrote: >> > Commit 73829af71fdb8655e7ba4b5a2a6612ad34a75a11 >> > (Merge branch 'vmalloc' of git://git.linaro.org/people/nico/linux >> > into devel-stable) merged generic ioremap changes. >> > >> > Commit 137d105d50f6e6c373c1aa759f59045e6239cf66 >> > (ARM: OMAP4: Fix errata i688 with MPU interconnect barriers) >> > added a workaround for omap4. >> > >> > In order for the errata to work, we now need the following >> > patch or else we'll get: >> > >> > kernel BUG at mm/vmalloc.c:1134! >> >> Oh my, I've just read this, and I'm extremely annoyed that this even hit >> mainline in the first place. It's utter crap. >> >> It's trying to use memblock to allocate memory _AFTER_ that memory has >> been passed on from memblock's control to other allocators. Calling >> memblock_alloc() at *any* initcall is Bad News (it _may_ appear to work >> but there's no way for memblock_alloc to tell anything else that the >> memory is being re-used.) >> >> Calling it and then trying to reserve it at ->map_io time is also Bad >> News - the memory at that point has already been mapped, and if you're >> expecting to be able to remap it with different attributes, you're going >> to double-map it with differing attributes. You lose. >> >> Not only that, but it's an abuse of the various callback functions into >> machine code. Don't do it. >> >> By all means, allocate the memory via memblock, but do it in the ->reserve >> callback. It's *exactly* what that callback is there for. The map it in >> the ->map_io callback. >> >> Don't try to be clever and abuse these callbacks. They aren't named just >> for fun and my delectation. They have *specific* purposes. Stick to >> those purposes in them and don't try to be clever, or you'll be moaned at. >> >> So, NAK. NAK for the original patch too. Do it properly. > > It seems I missed this detail when I quickly read through the original > patch last September, which is rather unfortunate. > > That doesn't stop this being completely the wrong approach though - and > being very very broken as it currently stands. May be I have missed you point but I thought below should remove the initial mapping. memblock_free(paddr, size); memblock_remove(paddr, size); This patch actually got under various versions. Indeed the first version did implement the ->reserve callback method but then it kept changing and you might have lost track of it. Regards Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
