[PATCH 6/24] [xen-unstable.hg] don't hard code xenstore/console domid when seeding grant table of new domU

[Alex Zeffertt <alex.zeffertt@eu.citrix.com>]

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This patch implements a way to determine in which domains the console
and xenstore daemons reside. If each of the files
/var/run/{console,xenstore}.did contains an integer, this integer is
interpreted as the domain id for that daemon. The default or fallback is
domid=0, of course. Here, libxc is modified to use this mechanism for
the grant table entries.

A previous version of this patch was sent to xen-devel. See
http://lists.xensource.com/archives/html/xen-devel/2008-07/msg00610.html

Signed-off-by: Diego Ongaro <diego.ongaro@citrix.com>
Signed-off-by: Alex Zeffertt <alex.zeffertt@eu.citrix.com>
---

diff -r 5ea8720ce31f tools/libxc/xc_dom_boot.c
--- a/tools/libxc/xc_dom_boot.c	Fri Aug 01 16:50:30 2008 +0100
+++ b/tools/libxc/xc_dom_boot.c	Fri Aug 01 16:50:31 2008 +0100
@@ -256,6 +256,31 @@
     return rc;
 }
 
+static uint32_t read_domid(const char *service)
+{
+    char buf[64];
+    int n;
+    FILE *f = NULL;
+    uint32_t domid = 0;
+
+    n = snprintf(buf, sizeof(buf), "/var/run/%s.did", service);
+    if ( n < 0 || n >= sizeof(buf) )
+        goto out;
+
+    f = fopen(buf, "r");
+    if ( f == NULL )
+        goto out;
+
+    if ( fscanf(f, "%" PRIu32, &domid) != 1 )
+        goto out;
+
+out:
+    if ( f != NULL )
+        fclose(f);
+
+    return domid;
+}
+
 static unsigned long xc_dom_gnttab_setup(int xc_handle, uint32_t domid)
 {
     DECLARE_HYPERCALL;
@@ -296,9 +321,8 @@
     unsigned long gnttab_gmfn;
     grant_entry_t *gnttab;
 
-    /* TODO: don't hard-code these */
-    console_domid = 0;
-    xenstore_domid = 0;
+    console_domid  = read_domid("console");
+    xenstore_domid = read_domid("xenstore");
 
     gnttab_gmfn = xc_dom_gnttab_setup(xc_handle, domid);
     if ( gnttab_gmfn == -1 )




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