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Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table
From: |
Ross Zwisler |
Subject: |
Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table |
Date: |
Fri, 28 Jul 2017 13:45:43 -0600 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
On Fri, Jul 28, 2017 at 11:11:10AM -0700, Dan Williams wrote:
> On Fri, Jul 28, 2017 at 11:04 AM, Ross Zwisler
> <address@hidden> 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?
- [Qemu-devel] QEMU NVDIMM as type 7 in e820 table, Ross Zwisler, 2017/07/28
- Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table, Dan Williams, 2017/07/28
- Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table,
Ross Zwisler <=
- Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table, Dan Williams, 2017/07/28
- Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table, Kani, Toshimitsu, 2017/07/28
- Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table, Haozhong Zhang, 2017/07/29
- Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table, Ross Zwisler, 2017/07/31
- Re: [Qemu-devel] QEMU NVDIMM as type 7 in e820 table, Igor Mammedov, 2017/07/31