On 07/28/17 13:45 -0600, Ross Zwisler wrote: > On Fri, Jul 28, 2017 at 11:11:10AM -0700, Dan Williams wrote: > > On Fri, Jul 28, 2017 at 11:04 AM, Ross Zwisler > > <ross.zwis...@linux.intel.com> wrote: > > > I've been using the virtualized NVDIMM support in QEMU for testing, and I > > > noticed that the physical addresses used by the virtual NVDIMMs aren't > > > present > > > in the guest's e820 table. > > > > > > Here is the e820 table on my QEMU instance where I have one 32 GiB virtual > > > NVDIMM: > > > > > > [ 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 0x0000000100000000-0x000000023fffffff] > > > usable > > > > > > The physical addresses used by the virtual NVDIMM are > > > 0x240000000-0xA40000000. > > > You can see this by looking at ndctl and the values we get from the NFIT: > > > > > > # ndctl list -R > > > { > > > "dev":"region0", > > > "size":34359738368, > > > "available_size":0, > > > "type":"pmem" > > > } > > > > > > # grep . /sys/bus/nd/devices/region0/{resource,size} > > > region0/resource:0x240000000 > > > region0/size:34359738368 > > > > > > Or you can see the same info by using iasl to dump > > > /sys/firmware/acpi/tables/NFIT: > > > > > > [028h 0040 2] Subtable Type : 0000 [System Physical > > > Address Range] > > > [02Ah 0042 2] Length : 0038 > > > > > > [02Ch 0044 2] Range Index : 0002 > > > [02Eh 0046 2] Flags (decoded below) : 0003 > > > Add/Online Operation Only : 1 > > > Proximity Domain Valid : 1 > > > [030h 0048 4] Reserved : 00000000 > > > [034h 0052 4] Proximity Domain : 00000000 > > > [038h 0056 16] Address Range GUID : > > > 66F0D379-B4F3-4074-AC43-0D3318B78CDB > > > [048h 0072 8] Address Range Base : 0000000240000000 > > > [050h 0080 8] Address Range Length : 0000000800000000 > > > [058h 0088 8] Memory Map Attribute : 0000000000008008 > > > > > > I expected to see a type 7 region for the NVDIMM physical address range > > > in the > > > e820 table, so something like: > > > > > > [ 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 0x0000000100000000-0x000000023fffffff] > > > usable > > > [ 0.000000] BIOS-e820: [mem 0x0000000240000000-0x0000000A40000000] > > > persistent (type 7) > > > > > > > Do you need that informationin e820? Linux effectively ignores type-7. > > As long as the range is treated as reserved it's not clear that you > > need the e820 entry. We also infect the persistent type back into the > > memory map when the NFIT driver loads. /proc/iomem should show the > > right data. > > [ Adding Linda & Toshi to see if they have an opinion. ] > > I guess maybe we don't need it. Yep, /proc/iomem looks good: > > # cat /proc/iomem > 00000000-00000fff : Reserved > 00001000-0009fbff : System RAM > ... > 100000000-23fffffff : System RAM > 240000000-a3fffffff : Persistent Memory > 240000000-a3fffffff : namespace0.0 > > I was just worried that this was an inconsistency between the way that virtual > NVDIMMs are presented vs the way that they will be presented on bare metal. I > at least look at the e820 table to get my bearings of how memory is laid out - > maybe I just need to look at /proc/iomem instead?
Do any OS or applications rely on the E820 information or the consistency between E820 and NFIT to properly work? If any, I can make a QEMU patch to build type-7 e820 entries. Haozhong _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm