xen: fix ram init regression

Commit "8156d48 pc: allow raising low memory via max-ram-below-4g
option" causes a regression on xen, because it uses a different
memory split.

This patch initializes max-ram-below-4g to zero and leaves the
initialization to the memory initialization functions.  That way
they can pick different default values (max-ram-below-4g is zero
still) or use the user supplied value (max-ram-below-4g is non-zero).

Also skip the whole ram split calculation on Xen.  xen_ram_init()
does its own split calculation anyway so it is superfluous, also
this way xen_ram_init can actually see whenever max-ram-below-4g
is zero or not.

Reported-by: Anthony PERARD <anthony.perard@citrix.com>
Tested-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/xen-hvm.c b/xen-hvm.c
index 98ea44fdf3..eb577926a1 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -190,6 +190,9 @@ static void xen_ram_init(PCMachineState *pcms,
     /* Handle the machine opt max-ram-below-4g.  It is basically doing
      * min(xen limit, user limit).
      */
+    if (!user_lowmem) {
+        user_lowmem = HVM_BELOW_4G_RAM_END; /* default */
+    }
     if (HVM_BELOW_4G_RAM_END <= user_lowmem) {
         user_lowmem = HVM_BELOW_4G_RAM_END;
     }