On Mon, Oct 22, 2012 at 1:26 PM, H. Peter Anvin <h...@linux.intel.com> wrote: >>>> 2. partial page: >>>> E820 or user could pass memmap that is not page aligned. >>>> old cold will guarded by max_low_pfn and max_pfn. so the end partial >>>> page will be trimmed down, and memblock can one use it. >>>> middle partial page will still get covered by directly mapping, and >>>> memblock still can use them. >>>> Now we will not map middle partial page and memblock still try to use it >>>> we could get panic when accessing those pages. >>>> >>>> So I would suggest to just revert that temporary patch at this time, >>>> and later come out one complete patch for stable kernels. >>> >>> Hm okay, I was hoping not, but if it has to be .. >> >> It's hpa's call. > > So the issue is that two E820 RAM ranges (or ACPI, or kernel-reserved) > are immediately adjacent on a non-page-aligned address?
yes. or the user take out range that is not page aligned. > Or is there a > gap in between and memblock is still expecting to use it? yes, current implementation is. and init_memory_mapping map those partial pages and holes. > > We should not map a partial page at the end of RAM; it is functionally > lost. Now we did not, we have max_low_pfn, and max_pfn to cap out end partial page. > Two immediately adjacent pages could be coalesced, but not a > partial page that abuts I/O space (and yes, such abortions can happen in > the real world.) > > However, the issue obviously is that what we can realistically put in > 3.7 or stable is limited at this point. ok, let's see if we can meet this extreme corner case except user specify not page aligned "memmap=" Thanks Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
