[PATCH v3] tools/helpers: don't log errors when trying to load PVH xenstore-stubdom

[Juergen Gross <jgross@xxxxxxxx>]

When loading a Xenstore stubdom the loader doesn't know whether the
lo be loaded kernel is a PVH or a PV one. So it tries to load it as
a PVH one first, and if this fails it is loading it as a PV kernel.

This results in errors being logged in case the stubdom is a PV kernel.

Suppress those errors by setting the minimum logging level to
"critical" while trying to load the kernel as PVH.

In case PVH mode and PV mode loading fails, retry PVH mode loading
without changing the log level in order to get the error messages
logged.

Fixes: f89955449c5a ("tools/init-xenstore-domain: support xenstore pvh stubdom")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- retry PVH loading with logging if PV fails, too (Jan Beulich)
V3:
- expand commit message (Jan Beulich)
- expand comment (Andrew Cooper)
---
 tools/helpers/init-xenstore-domain.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/tools/helpers/init-xenstore-domain.c 
b/tools/helpers/init-xenstore-domain.c
index 04e351ca29..85cc9e8381 100644
--- a/tools/helpers/init-xenstore-domain.c
+++ b/tools/helpers/init-xenstore-domain.c
@@ -31,6 +31,8 @@ static int memory;
 static int maxmem;
 static xen_pfn_t console_gfn;
 static xc_evtchn_port_or_error_t console_evtchn;
+static xentoollog_level minmsglevel = XTL_PROGRESS;
+static void *logger;
 
 static struct option options[] = {
     { "kernel", 1, NULL, 'k' },
@@ -141,19 +143,33 @@ static int build(xc_interface *xch)
         goto err;
     }
 
+    /*
+     * This is a bodge.  We can't currently inspect the kernel's ELF notes
+     * ahead of attempting to construct a domain, so try PVH first, suppressing
+     * errors by setting min level to high, and fall back to PV.
+     */
     dom->container_type = XC_DOM_HVM_CONTAINER;
+    xtl_stdiostream_set_minlevel(logger, XTL_CRITICAL);
     rv = xc_dom_parse_image(dom);
+    xtl_stdiostream_set_minlevel(logger, minmsglevel);
     if ( rv )
     {
         dom->container_type = XC_DOM_PV_CONTAINER;
         rv = xc_dom_parse_image(dom);
         if ( rv )
         {
-            fprintf(stderr, "xc_dom_parse_image failed\n");
-            goto err;
+            /* Retry PVH, now with normal logging level. */
+            dom->container_type = XC_DOM_HVM_CONTAINER;
+            rv = xc_dom_parse_image(dom);
+            if ( rv )
+            {
+                fprintf(stderr, "xc_dom_parse_image failed\n");
+                goto err;
+            }
         }
     }
-    else
+
+    if ( dom->container_type == XC_DOM_HVM_CONTAINER )
     {
         config.flags |= XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap;
         config.arch.emulation_flags = XEN_X86_EMU_LAPIC;
@@ -412,8 +428,6 @@ int main(int argc, char** argv)
     char buf[16], be_path[64], fe_path[64];
     int rv, fd;
     char *maxmem_str = NULL;
-    xentoollog_level minmsglevel = XTL_PROGRESS;
-    xentoollog_logger *logger = NULL;
 
     while ( (opt = getopt_long(argc, argv, "v", options, NULL)) != -1 )
     {
@@ -456,9 +470,7 @@ int main(int argc, char** argv)
         return 2;
     }
 
-    logger = (xentoollog_logger *)xtl_createlogger_stdiostream(stderr,
-                                                               minmsglevel, 0);
-
+    logger = xtl_createlogger_stdiostream(stderr, minmsglevel, 0);
     xch = xc_interface_open(logger, logger, 0);
     if ( !xch )
     {
-- 
2.35.3