[Xen-devel] [PATCH 26/26] xl: Document VGA problems arising from lack of physmap dmop

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

Ross reports that stdvga guests do not work, and cirrus guests are
slow, because qemu tries to do xc_domain_add_to_physmap.  We will need
another dmop to fix this properly.

For now, document the problem.

(In the cirrus case, the vram remains mapped at the old guest-physical
addresses, while the guest runs.  We are not sure whether this is a
correctness or security problem and we should advise against it.)

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Reported-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
CC: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
 docs/man/xl.cfg.pod.5.in | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/docs/man/xl.cfg.pod.5.in b/docs/man/xl.cfg.pod.5.in
index cb32d04..cf3fa0e 100644
--- a/docs/man/xl.cfg.pod.5.in
+++ b/docs/man/xl.cfg.pod.5.in
@@ -2242,6 +2242,12 @@ For example, cdrom insert will fail.
 
 =item
 
+You should say C<vga="none">.
+Domains with stdvga graphics cards to not work.
+Domains with cirrus vga may seem to work.
+
+=item
+
 You must create user(s) for qemu to run as.
 
 Ideally, set aside a range of 32752 uids
-- 
2.1.4


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