From: Anthony PERARD <anthony.perard@citrix.com>
To: qemu-devel@nongnu.org
Cc: xen-devel@lists.xen.org,
Stefano Stabellini <sstabellini@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Gerd Hoffmann <kraxel@redhat.com>
Subject: [Qemu-devel] Change of max-ram-below-4g initial value breaks Xen
Date: Wed, 22 Jun 2016 16:09:37 +0100 [thread overview]
Message-ID: <20160622150937.GS5666@perard.uk.xensource.com> (raw)
Hi,
following commit 8156d48 (pc: allow raising low memory via
max-ram-below-4g option), guest under Xen fail to boot. This is due to
the initial value of max-ram-below-4g been change from 4G to 3.5G.
Unfortunately, a Xen guest have a higher default split, at 3.75G, but
can be change via the -machine options max-ram-below-4g. Now, it looks
like a user ask for 3.5G where the rest of the Xen tool stack is still
at 3.75G.
In QEMU, the ram split calculation for Xen is done in xen_ram_init(). It
can be change via max-ram-below-4g.
The hvmloader firmware will start the MMIO hole at 3.75G unless told
otherwise via a xenstore entry. The xenstore entry can be set by the Xen
toolstack, which would also add 'max-ram-below-4g' to -machine if a user
request it.
How could xen_ram_init() find out if the value of max-ram-below-4g is
the default or if a user have set it? Is there another way we could fix
this?
Regards,
--
Anthony PERARD
WARNING: multiple messages have this Message-ID (diff)
From: Anthony PERARD <anthony.perard@citrix.com>
To: qemu-devel@nongnu.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Gerd Hoffmann <kraxel@redhat.com>,
xen-devel@lists.xen.org
Subject: Change of max-ram-below-4g initial value breaks Xen
Date: Wed, 22 Jun 2016 16:09:37 +0100 [thread overview]
Message-ID: <20160622150937.GS5666@perard.uk.xensource.com> (raw)
Hi,
following commit 8156d48 (pc: allow raising low memory via
max-ram-below-4g option), guest under Xen fail to boot. This is due to
the initial value of max-ram-below-4g been change from 4G to 3.5G.
Unfortunately, a Xen guest have a higher default split, at 3.75G, but
can be change via the -machine options max-ram-below-4g. Now, it looks
like a user ask for 3.5G where the rest of the Xen tool stack is still
at 3.75G.
In QEMU, the ram split calculation for Xen is done in xen_ram_init(). It
can be change via max-ram-below-4g.
The hvmloader firmware will start the MMIO hole at 3.75G unless told
otherwise via a xenstore entry. The xenstore entry can be set by the Xen
toolstack, which would also add 'max-ram-below-4g' to -machine if a user
request it.
How could xen_ram_init() find out if the value of max-ram-below-4g is
the default or if a user have set it? Is there another way we could fix
this?
Regards,
--
Anthony PERARD
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Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next reply other threads:[~2016-06-22 15:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-22 15:09 Anthony PERARD [this message]
2016-06-22 15:09 ` Change of max-ram-below-4g initial value breaks Xen Anthony PERARD
2016-06-22 15:27 ` [Qemu-devel] " Gerd Hoffmann
2016-06-22 15:27 ` Gerd Hoffmann
2016-06-23 14:57 ` [Qemu-devel] " Gerd Hoffmann
2016-06-23 14:57 ` Gerd Hoffmann
2016-06-23 16:18 ` [Qemu-devel] " Anthony PERARD
2016-06-23 16:18 ` Anthony PERARD
2016-06-24 5:46 ` [Qemu-devel] " Gerd Hoffmann
2016-06-24 11:19 ` Anthony PERARD
2016-06-24 11:19 ` Anthony PERARD
2016-06-24 5:46 ` Gerd Hoffmann
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