On Mon, Mar 7, 2016 at 9:56 AM, Toshi Kani <toshi.kani@xxxxxxx> wrote: > On Fri, 2016-03-04 at 18:23 -0800, Dan Williams wrote: >> On Fri, Mar 4, 2016 at 6:48 PM, Toshi Kani <toshi.kani@xxxxxxx> wrote: [..] >> As far as I can see >> all we do is ask firmware implementations to respect Linux section >> boundaries and otherwise not change alignments. > > In addition to the requirement that pmem range alignment may not change, > the code also requires a regular memory range does not change to intersect > with a pmem section later. This seems fragile to me since guest config may > vary / change as I mentioned above. > > So, shouldn't the driver fails to attach when the range is not aligned by > the section size? Since we need to place a requirement to firmware anyway, > we can simply state that it must be aligned by 128MiB (at least) on x86. > Then, memory and pmem physical layouts can be changed as long as this > requirement is met. We can state that it must be aligned, but without a hard specification I don't see how we can guarantee it. We will fail the driver load with a warning if our alignment fixups end up getting invalidated by a later configuration change, but in the meantime we cover the gap of a BIOS that has generated a problematic configuration. -- 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>