replace stat("/etc/disable-guest-log-throttle") in xen_platform.c

currently xen_platform reads /etc/disable-guest-log-throttle at boot to
decide whether is going to throttle guest logging or not.
When using stubdom this is the only code in qemu that rely on
fs-backend, apart from saving and loading the statefile for migration.
This patch removes the read from /etc and adds a read from xenstore
instead.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
(cherry picked from commit e17ca57cf5e6d4c6d11eccca7daee853915a6eff)

diff --git a/hw/xen_platform.c b/hw/xen_platform.c
index 9827e3f6195daf658eb7bc8bfb068c8466600477..36610a4406dfcb45c618162d9e198fdaf72d1109 100644 (file)
--- a/hw/xen_platform.c
+++ b/hw/xen_platform.c
@@ -276,6 +276,8 @@ static int platform_fixed_ioport_load(QEMUFile *f, void *opaque, int version_id)
 void platform_fixed_ioport_init(void)
 {
     struct stat stbuf;
+    char *throttling;
+    int len = 1;
 
     register_savevm("platform_fixed_ioport", 0, 1, platform_fixed_ioport_save,
                     platform_fixed_ioport_load, NULL);
@@ -286,8 +288,11 @@ void platform_fixed_ioport_init(void)
     register_ioport_read(0x10, 16, 2, platform_fixed_ioport_read2, NULL);
     register_ioport_read(0x10, 16, 1, platform_fixed_ioport_read1, NULL);
 
-    if (stat("/etc/disable-guest-log-throttle", &stbuf) == 0)
-        throttling_disabled = 1;
+    throttling = xenstore_vm_read(domid, "log-throttling", &len);
+    if (throttling != NULL) {
+        throttling_disabled = (throttling[0] - '0');
+        free(throttling);
+    }
 
     platform_fixed_ioport_write1(NULL, 0x10, 0);
 }