Re: [Xen-devel] real physical e820 table for dom0?

[Gordan Bobic <gordan@xxxxxxxxxx>]

I was under the impression that dom0 should always have the
real e820 map. If you limit it's memory, the memory gets
truncated at the point where that much real RAM is allocated,
but the reserved areas and holes should remain as per the
physical map.

Is that not what is expected?

Gordan

On 2014-03-06 08:45, Zhang, Yang Z wrote:
> Hi all,
>
> I have 8G memory in hardware and I only give 2G memory to dom0. The
> information from /proc/meminfo shows the total memory is about 2G
> which should be correct. But the memory information from sysrq is
> wrong (see below). It shows the total memory is 8G(2015427 pages)
> which I thought should be 2G also. After a little investigation, I
> found currently dom0 using the real physical e820 map which I remember
> should be a pseudo-e820 map provided by Xen long time ago.
>
> Here is my e820 table:
> [    0.000000] e820: BIOS-provided physical RAM map:
> [    0.000000] Xen: [mem 0x0000000000000000-0x000000000009cfff] usable
> [    0.000000] Xen: [mem 0x000000000009d800-0x00000000000fffff] 
> reserved
> [    0.000000] Xen: [mem 0x0000000000100000-0x00000000b9775fff] usable
> [    0.000000] Xen: [mem 0x00000000b9776000-0x00000000b977cfff] ACPI 
> NVS
> [    0.000000] Xen: [mem 0x00000000b977d000-0x00000000b9bc2fff] usable
> [    0.000000] Xen: [mem 0x00000000b9bc3000-0x00000000b9fdcfff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000b9fdd000-0x00000000cc746fff] usable
> [    0.000000] Xen: [mem 0x00000000cc747000-0x00000000cc94cfff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000cc94d000-0x00000000cc961fff] ACPI 
> data
> [    0.000000] Xen: [mem 0x00000000cc962000-0x00000000cce03fff] ACPI 
> NVS
> [    0.000000] Xen: [mem 0x00000000cce04000-0x00000000cdffefff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000cdfff000-0x00000000cdffffff] usable
> [    0.000000] Xen: [mem 0x00000000cf000000-0x00000000df1fffff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000f8000000-0x00000000fbffffff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000fec00000-0x00000000fec00fff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000fed00000-0x00000000fed03fff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000fed1c000-0x00000000fed1ffff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000fee00000-0x00000000feefffff] 
> reserved
> [    0.000000] Xen: [mem 0x00000000ff000000-0x00000000ffffffff] 
> reserved
> [    0.000000] Xen: [mem 0x0000000100000000-0x000000021fdfffff] usable
> [    0.000000] NX (Execute Disable) protection: active
> [    0.000000] SMBIOS 2.7 present.
> [    0.000000] DMI: ASUS All Series/Z87-PRO, BIOS 0801 04/19/2013
> [    0.000000] e820: update [mem 0x00000000-0x00000fff] usable ==> 
> reserved
> [    0.000000] e820: remove [mem 0x000a0000-0x000fffff] usable
> [    0.000000] e820: last_pfn = 0x21fe00 max_arch_pfn = 0x400000000
> [    0.000000] e820: last_pfn = 0xce000 max_arch_pfn = 0x400000000
>
> Obviously, now dom0 sees the whole physical memory map and the
> last_pfn is 0x21fe00 which exceed the 2G bound. I wonder why using the
> real physical memory map? At least now the sysrq is showing wrong
> output.
>
> Here is the changeset to use the physical E820 table:
>
> commit 9e9a5fcb04e3af077d1be32710298b852210d93f
> Author: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Date:   Thu Sep 2 16:16:00 2010 +0100
>
>     xen: use host E820 map for dom0
>
>     When running as initial domain, get the real physical memory map 
> from
>     xen using the XENMEM_machine_memory_map hypercall and use it to 
> setup
>     the e820 regions.
>
> memory info from sysrq:
> [   97.145517] SysRq : Show Memory
> [   97.146701] Mem-Info:
> [   97.147502] DMA per-cpu:
> [   97.148389] CPU    0: hi:    0, btch:   1 usd:   0
> [   97.150070] CPU    1: hi:    0, btch:   1 usd:   0
> [   97.151750] CPU    2: hi:    0, btch:   1 usd:   0
> [   97.153422] CPU    3: hi:    0, btch:   1 usd:   0
> [   97.155093] DMA32 per-cpu:
> [   97.156041] CPU    0: hi:  186, btch:  31 usd: 179
> [   97.157718] CPU    1: hi:  186, btch:  31 usd:  45
> [   97.159393] CPU    2: hi:  186, btch:  31 usd: 142
> [   97.160324] CPU    3: hi:  186, btch:  31 usd: 153
> [   97.160713] Normal per-cpu:
> [   97.160940] CPU    0: hi:    0, btch:   1 usd:   0
> [   97.161326] CPU    1: hi:    0, btch:   1 usd:   0
> [   97.161715] CPU    2: hi:    0, btch:   1 usd:   0
> [   97.162103] CPU    3: hi:    0, btch:   1 usd:   0
> [   97.162492] active_anon:54690 inactive_anon:984 isolated_anon:0
> [   97.162492]  active_file:25003 inactive_file:48300 isolated_file:0
> [   97.162492]  unevictable:2 dirty:323 writeback:0 unstable:0
> [   97.162492]  free:569113 slab_reclaimable:7449 
> slab_unreclaimable:5467
> [   97.162492]  mapped:15956 shmem:1098 pagetables:10222 bounce:0
> [   97.162492]  free_cma:0
> [   97.165045] DMA free:12764kB min:36kB low:44kB high:52kB
> active_anon:1196kB inactive_anon:12kB active_file:516kB
> inactive_file:860kB unevictable:0kB isolated(anon):0kB
> isolated(file):0kB present:15984kB managed:15896kB mlocked:0kB
> dirty:12kB writeback:0kB mapped:288kB shmem:12kB
> slab_reclaimable:160kB slab_unreclaimable:72kB kernel_stack:32kB
> pagetables:220kB unstable:0kB bounce:0kB free_cma:0kB
> writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
> [   97.168243] lowmem_reserve[]: 0 2818 2818 2818
> [   97.168676] DMA32 free:2263688kB min:6772kB low:8464kB high:10156kB
> active_anon:217564kB inactive_anon:3924kB active_file:99496kB
> inactive_file:192340kB unevictable:8kB isolated(anon):0kB
> isolated(file):0kB present:3329180kB managed:2890396kB mlocked:8kB
> dirty:1280kB writeback:0kB mapped:63536kB shmem:4380kB
> slab_reclaimable:29636kB slab_unreclaimable:21796kB
> kernel_stack:2560kB pagetables:40668kB unstable:0kB bounce:0kB
> free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
> [   97.244293] lowmem_reserve[]: 0 0 0 0
> [   97.270081] Normal free:0kB min:0kB low:0kB high:0kB
> active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB
> unevictable:0kB isolated(anon):0kB isolated(file):0kB
> present:4716544kB managed:0kB mlocked:0kB dirty:0kB writeback:0kB
> mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB
> kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB free_cma:0kB
> writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
> [   97.355942] lowmem_reserve[]: 0 0 0 0
> [   97.384106] DMA: 2*4kB (U) 1*8kB (U) 1*16kB (M) 2*32kB (EM) 2*64kB
> (EM) 2*128kB (UM) 2*256kB (EM) 1*512kB (E) 3*1024kB (UEM) 2*2048kB
> (ER) 1*4096kB (M) = 12768kB
> [   97.414040] DMA32: 132*4kB (UM) 121*8kB (UEM) 71*16kB (UEM) 18*32kB
> (UEM) 2*64kB (UE) 4*128kB (UE) 2*256kB (U) 3*512kB (U) 1*1024kB (U)
> 2*2048kB (EM) 550*4096kB (MR) = 2263816kB
> [   97.444916] Normal: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB
> 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 0kB
> [   97.476175] Node 0 hugepages_total=0 hugepages_free=0
> hugepages_surp=0 hugepages_size=2048kB
> [   97.508023] 74406 total pagecache pages
> [   97.539701] 0 pages in swap cache
> [   97.571126] Swap cache stats: add 0, delete 0, find 0/0
> [   97.602918] Free swap  = 10485756kB
> [   97.634737] Total swap = 10485756kB
> [   97.666398] 2015427 pages RAM
> [   97.697824] 0 pages HighMem/MovableOnly
> [   97.729134] 1179136 pages reserved
>
> best regards
> yang
>
>
>
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