Re: [Xen-devel] [Xen-users] xl info displays less ram than the total available

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 05/10/16 14:02, George Dunlap wrote:
> On 05/10/16 13:52, blallo@xxxxxxxxxx wrote:
>> George Dunlap:
>>> On Wed, Oct 5, 2016 at 11:16 AM,  <blallo@xxxxxxxxxx> wrote:
>>>> Hi all,
>>>> I have been wondering if I could manage to make Xen function on my
>>>> laptop, using as dom0 my Arch Linux installation. As far as I understood
>>>> there is no currently supported package in the AUR nor, obviously, in
>>>> the official repos. What to do? Compile it by myself! I went under all
>>>> the process, in particular
>>>>
>>>> % PYTHON="/usr/bin/python2" ./configure --enable-stubdom \
>>>>                --enable-systemd --prefix=/usr
>>>>
>>>> % PYTHON="/usr/bin/python2" NO_WERROR=1 make dist
>>>>
>>>> % sudo PYTHON="/usr/bin/python2" NO_WERROR=1 make install
>>>>
>>>> After that I manually added a grub entry to boot into my dom0
>>>> chainbooted by Xen.
>>>>
>>>> And it seemed I succeeded, as far as I manage to boot into my system.
>>>> Everything seem to work, except that if I look at the features of my
>>>> system
>>>>
>>>> % sudo xl info
>>>>
>>>> I get a discouraging indication on the total amount of ram I have on my
>>>> system
>>>>
>>>> total_memory           : 1948
>>>> free_memory            : 120
>>>>
>>>> while the total memory is (as measured from Arch booted without Xen)
>>>>
>>>> % free -m
>>>>            total       used     free     shared  buff/cache  available
>>>>    Mem:    15924       8756     2206     737     4961        6100
>>>>    Swap:   8191        0        8191
>>>>
>>>> What to do? I am very new to Xen, how can I debug it?
>>> Thanks for your report.  Can you please attach the full output of "xl
>>> info", as well as the output of "xl dmesg"?
>>>
>>> Thanks,
>>> -George
>> I attach the output of xl info, xl dmesg in dom0 *and* dmesg in a normal
>> Arch Linux boot (without Xen).
> That's quite strange -- the e820 maps reported by Linux and Xen appear
> to be almost completely different:
>
> (XEN) Xen-e820 RAM map:
> (XEN)  0000000000000000 - 000000000009ec00 (usable)
> (XEN)  000000000009ec00 - 00000000000a0000 (reserved)
> (XEN)  00000000000e0000 - 0000000000100000 (reserved)
> (XEN)  0000000000100000 - 0000000079cbe000 (usable)
> (XEN)  0000000079cbe000 - 00000000bcd2f000 (reserved)
> (XEN)  00000000bcd2f000 - 00000000bce7f000 (ACPI NVS)
> (XEN)  00000000bce7f000 - 00000000bceff000 (ACPI data)
> (XEN)  00000000bceff000 - 00000000bfa00000 (reserved)
> (XEN)  00000000f8000000 - 00000000fc000000 (reserved)
> (XEN)  00000000fec00000 - 00000000fec01000 (reserved)
> (XEN)  00000000fed08000 - 00000000fed09000 (reserved)
> (XEN)  00000000fed10000 - 00000000fed1a000 (reserved)
> (XEN)  00000000fed1c000 - 00000000fed20000 (reserved)
> (XEN)  00000000fee00000 - 00000000fee01000 (reserved)
> (XEN)  00000000ffc00000 - 000000043e600000 (reserved)
>
> BIOS-e820: [mem 0x0000000000000000-0x0000000000057fff] usable
> BIOS-e820: [mem 0x0000000000058000-0x0000000000058fff] reserved
> BIOS-e820: [mem 0x0000000000059000-0x000000000008bfff] usable
> BIOS-e820: [mem 0x000000000008c000-0x00000000000bffff] reserved
> BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
> BIOS-e820: [mem 0x0000000000100000-0x000000007b82dfff] usable
> BIOS-e820: [mem 0x000000007b82e000-0x000000007ba2ffff] reserved
> BIOS-e820: [mem 0x000000007ba30000-0x00000000ba1fcfff] usable
> BIOS-e820: [mem 0x00000000ba1fd000-0x00000000ba3fcfff] type 20
> BIOS-e820: [mem 0x00000000ba3fd000-0x00000000bcd2efff] reserved
> BIOS-e820: [mem 0x00000000bcd2f000-0x00000000bce7efff] ACPI NVS
> BIOS-e820: [mem 0x00000000bce7f000-0x00000000bcefefff] ACPI data
> BIOS-e820: [mem 0x00000000bceff000-0x00000000bcefffff] usable
> BIOS-e820: [mem 0x00000000bcf00000-0x00000000bf9fffff] reserved
> BIOS-e820: [mem 0x00000000f80f8000-0x00000000f80f8fff] reserved
> BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> BIOS-e820: [mem 0x0000000100000000-0x000000043e5fffff] usable
>
> With the key thing being that Xen's version has the range from ~2G-3G
> and 4G-17G as 'reserved', while Linux's version has those ranges as
> 'usable'.
>
> Jan / Andy, any idea what's going on here?

Not specifically.  Can you boot with e820-verbose on the Xen command
line, which will provide more information?

~Andrew

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