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.... Cheers, Dave. -- Dave Chinner [email protected]
