[Xen-devel] Question to Xen log level in the case of PT

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

All guys,

Sorry to raise a question to you since I'm not very sure how to deal 
with this.
When I passthrough a device like IGD, I can see so many messages:

"memory_map:add:...." and "memory_map:remove:"

since we have to add/remove all pages map residing PCI bar. Especially 
as a graphic device, oftentimes this range would occupy dozens of MB, 
even hundreds of MB. These print messages consume a lot of time to boot 
a VM. For instance, it takes about 5 minutes to boot a Windows guest on 
my BDW. But if I remove these output simply like this,
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 7f959f3..82da9d1 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -1049,10 +1049,6 @@ long 
do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
         if ( add )
         {
-            printk(XENLOG_G_INFO
-                   "memory_map:add: dom%d gfn=%lx mfn=%lx nr=%lx\n",
-                   d->domain_id, gfn, mfn, nr_mfns);
-
             ret = map_mmio_regions(d, gfn, nr_mfns, mfn);
             if ( ret )
                 printk(XENLOG_G_WARNING
@@ -1061,10 +1057,6 @@ long 
do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
         }
         else
         {
-            printk(XENLOG_G_INFO
-                   "memory_map:remove: dom%d gfn=%lx mfn=%lx nr=%lx\n",
-                   d->domain_id, gfn, mfn, nr_mfns);
-
             ret = unmap_mmio_regions(d, gfn, nr_mfns, mfn);
             if ( ret && is_hardware_domain(current->domain) )
                 printk(XENLOG_ERR

its down to a half, about 2.5 minutes.

I know I can't delete this directly. But currently there are four log 
level on Xen side,
 *   XENLOG_ERR: Fatal errors, either Xen, Guest or Dom0
 *               is about to crash.
 *
 *   XENLOG_WARNING: Something bad happened, but we can recover.
 *
 *   XENLOG_INFO: Interesting stuff, but not too noisy.
 *
 *   XENLOG_DEBUG: Use where ever you like. Lots of noise.

looks I have to change XENLOG_G_INFO to XENLOG_G_WARNING but its not 
appropriate here.
So can Xen change log level dynamically like Linux? If yes, we might 
change this level temporarily while passing through IGD. If not, any 
suggestion?
Thanks
Tiejun

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