On Sun, Nov 1, 2015 at 8:11 AM, Ian Lepore <i...@freebsd.org> wrote:
> > It's almost certainly not related to sysinit ordering. This exception > is happening during mmc probing after interrupts are enabled. > > It appears that the problem is the faulting code is running on one of > the very early pre-allocated kernel stacks (perhaps in an interrupt > handler on an idle thread stack), and these stacks are not in memory > represented in the vm page arrays. The mmc code is using a 64-byte > buffer on the stack and mapping it for DMA. Normally that causes a > bounce for cacheline alignment, but unluckily in this case that buffer > on the stack just happened to be aligned to a cacheline boundary and a > multiple of the cacheline size, so no bounce. That causes the new sync > logic that is based on keeping vm_page_t pointers and offsets to get a > NULL pointer back from PHYS_TO_VM_PAGE when mapping, then it dies at > sync time trying to dereference that. It used to work because the sync > logic used to use the vaddr, not a page pointer. > > Michal was working on a patch yesterday. > > Ah, thanks for pointing that out Ian. I was left scratching my head (admittedly on the road and w/o easy access to the code) wondering what on earth would be trying to do DMA during SI_SUB_CPU. _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
