From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony PERARD <anthony.perard@citrix.com>
Subject: Can't create small PV guest anymore (64MB)
Date: Mon, 8 Feb 2016 11:18:10 +0000
Message-ID: <20160208111810.GA1810@perard.uk.xensource.com>
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To: Xen Devel <xen-devel@lists.xen.org>, Ian Campbell <ian.campbell@citrix.com>, Juergen Gross <jgross@suse.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, Wei Liu <wei.liu2@citrix.com>
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Hi,

I used to be able to boot a guest with 64MB, but now the minimum required
to boot it seams to be 85MB. It's a PV guest used and lauched by OpenStack
with there test suite. You can find the image at [1].

The guest failed to boot with this error message:
xc: error: panic: xc_dom_x86.c:147: count_pgtables: not enough memory for initial mapping (0x5498 > 0x4000): Out of memory
libxl: error: libxl_dom.c:655:libxl__build_dom: xc_dom_build_image failed: No such file or directory
...

It still works on commit 6853c9b but guest creation fail on commit d07f63f.
In between, there is a patch series from Juergen that change libxc. I have
not check which patch in particular broke guest creation.

How can we boot this guest [1] with only 64MB of memory like it was working
before?

[1] http://download.cirros-cloud.net/0.3.4/cirros-0.3.4-x86_64-uec.tar.gz

-- 
Anthony PERARD