On Tue, Oct 11, 2016 at 4:31 PM, Dave Chinner <da...@fromorbit.com> wrote: > Hi Dan, > > I boot my DAX test machine with "memmap=8G!16G,8G!24G" on the kernel > command line to give me two 8GB pmem devices. This has worked fine > on all kernels including 4.8. I just updated that test machine to a > TOT linus kernel (4.9), and now I get a single 16GB pmem device. > i.e. the memory map the kernel generates is different. This is > what I get on boot from a 4.9 kernel: > > [ 0.000000] e820: BIOS-provided physical RAM map: > [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable > [ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved > [ 0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000bffdefff] usable > [ 0.000000] BIOS-e820: [mem 0x00000000bffdf000-0x00000000bfffffff] reserved > [ 0.000000] BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved > [ 0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved > [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000083fffffff] usable > [ 0.000000] NX (Execute Disable) protection: active > [ 0.000000] e820: user-defined physical RAM map: > [ 0.000000] user: [mem 0x0000000000000000-0x000000000009fbff] usable > [ 0.000000] user: [mem 0x000000000009fc00-0x000000000009ffff] reserved > [ 0.000000] user: [mem 0x00000000000f0000-0x00000000000fffff] reserved > [ 0.000000] user: [mem 0x0000000000100000-0x00000000bffdefff] usable > [ 0.000000] user: [mem 0x00000000bffdf000-0x00000000bfffffff] reserved > [ 0.000000] user: [mem 0x00000000feffc000-0x00000000feffffff] reserved > [ 0.000000] user: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved > [ 0.000000] user: [mem 0x0000000100000000-0x00000003ffffffff] usable > [ 0.000000] user: [mem 0x0000000400000000-0x00000007ffffffff] persistent > (type 12) > [ 0.000000] user: [mem 0x0000000800000000-0x000000083fffffff] usable > > > On 4.8, I get two persistent (type 12) sections, each of 8GB. 4.9 is > giving me a single 16GB region. This needs to behave like a 4.8 > kernel and return two persistent regions - persistent memory device > setup cannot be allowed to change from kernel to kernel. Change in > mapping and device setup like this will cause the corruption of > and/or loss of data in the persistent memory devices that have > changed shape, size or disappeared.... >
I wonder if this is a side effect of: 917db484dc6a x86/boot: Fix kdump, cleanup aborted E820_PRAM max_pfn manipulation Can you retry reverting that? If that does not fix it I'll take a look at bisecting this.