On Mon, Jul 27, 2015 at 02:19:11PM +0800, Lin Ma wrote:

在 2015年07月27日 13:34, Martin Kletzander 写道:

On Mon, Jul 27, 2015 at 12:48:50PM +0800, Lin Ma wrote:

Return 16M for qxl because QEMU uses 16MB as the default video ram size
for qxl device since pc-1.2.

NACK, that function is not meant to return the default video ram size
of QEMU, but rather video ram size that libvirt will set by default.

For qxl, The return value of that function is used to set ram and vram
attributes which
qemu doesn't care of. The proper and effective attribute is vgamem
which was set
to 16M already(commit#0e50246).

It causes the strange attribute list in guest xml:
 <video>
     <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1'/>
     ......
  </video>

and virt-manager also shows the inproper video ram size for qxl, It
shows 64MB
qxl video ram size in guest detailed page, but guest reports only 16MB.

So should I keep 64MB in virDomainVideoDefaultRAM and set vgamem by
virDomainVideoDefaultRAM?
Or something else?

Well, in this case, I think the aim was to set everything to 64MB, but
I remember some migration problems needed to be taken care of.  So
maybe we need to keep it for some reason.  To be sure, I'll let Pavel
handle this as he dealt with all the stuff related.  But we need to be
consistent and be able to migrate from older versions that had these
attributes set.  Also if this change needs to be done for QEMU, it
should be somewhere in src/qemu and not in src/conf where it changes
behaviour for all drivers.

Signed-off-by: Lin Ma <lma@suse.com>
---
src/conf/domain_conf.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 6b557d1..8efc973 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -11651,8 +11651,10 @@ virDomainVideoDefaultRAM(const
virDomainDef *def,
       return 4 * 1024;

   case VIR_DOMAIN_VIDEO_TYPE_QXL:
-        /* QEMU use 64M as the minimal video memory for qxl device */
-        return 64 * 1024;
+        /* By default, QEMU uses 16MB as video memory size
+         * for qxl device since pc-1.2
+         */
+        return 16 * 1024;

   default:
       return 0;
--
2.1.4

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