On 02/08/2013 12:28 PM, Dave Hansen wrote:
I was auding the /dev/mem code for more questionable uses of __pa(), and ran across this. My assumption is that if you use /dev/kmem, you expect to be able to read the kernel virtual mappings. However, those mappings _stop_ as soon as we hit high memory. The pfn_valid() check in here is good for memory holes, but since highmem pages are still valid, it does no good for those. Also, since we are now checking that __pa() is being done on valid virtual addresses, this might have tripped the new check. Even with the new check, this code would have been broken with the NUMA remapping code had we not ripped it out:
It would be great if you could take a stab at fixing /dev/mem and /dev/kmem... there are a bunch of problems with both which seem to really translate to "HIGHMEM was never properly implemented"...
-hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>