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)
Thanks,
- Ross
