[Xen-devel] [PATCH v4 4/5] libxl: update vcpus bitmap in retrieved guest config

[Wei Liu <wei.liu2@xxxxxxxxxx>]

... because the available vcpu bitmap can change during domain life time
due to cpu hotplug and unplug.

For QEMU upstream, we interrogate QEMU for the number of vcpus. For
others, we look directly into xenstore for information.

Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>

v4:
1. Use libxl__device_model_version_running
2. Move comment

v3:
1. Fix indentation of abort.
2. Use strcmp instead of strncmp.
---
 tools/libxl/libxl.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 51d202f..3786b09 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -7249,6 +7249,53 @@ void libxl_mac_copy(libxl_ctx *ctx, libxl_mac *dst, 
const libxl_mac *src)
         (*dst)[i] = (*src)[i];
 }
 
+/* For QEMU upstream we always need to provide the number of cpus present to
+ * QEMU whether they are online or not; otherwise QEMU won't accept the saved
+ * state. See implementation of libxl__qmp_query_cpus.
+ */
+static int libxl__update_avail_vcpus_qmp(libxl__gc *gc, uint32_t domid,
+                                         unsigned int max_vcpus,
+                                         libxl_bitmap *map)
+{
+    int rc;
+
+    rc = libxl__qmp_query_cpus(gc, domid, map);
+    if (rc) {
+        LOG(ERROR, "fail to get number of cpus for domain %d", domid);
+        goto out;
+    }
+
+    rc = 0;
+out:
+    return rc;
+}
+
+static int libxl__update_avail_vcpus_xenstore(libxl__gc *gc, uint32_t domid,
+                                              unsigned int max_vcpus,
+                                              libxl_bitmap *map)
+{
+    int rc;
+    unsigned int i;
+    const char *dompath;
+
+    dompath = libxl__xs_get_dompath(gc, domid);
+    if (!dompath) {
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    for (i = 0; i < max_vcpus; i++) {
+        const char *path = GCSPRINTF("%s/cpu/%u/availability", dompath, i);
+        const char *content = libxl__xs_read(gc, XBT_NULL, path);
+        if (!strcmp(content, "online"))
+            libxl_bitmap_set(map, i);
+    }
+
+    rc = 0;
+out:
+    return rc;
+}
+
 int libxl_retrieve_domain_configuration(libxl_ctx *ctx, uint32_t domid,
                                         libxl_domain_config *d_config)
 {
@@ -7297,6 +7344,49 @@ int libxl_retrieve_domain_configuration(libxl_ctx *ctx, 
uint32_t domid,
         libxl_dominfo_dispose(&info);
     }
 
+    /* VCPUs */
+    {
+        libxl_bitmap *map = &d_config->b_info.avail_vcpus;
+        unsigned int max_vcpus = d_config->b_info.max_vcpus;
+        libxl_device_model_version version;
+
+        libxl_bitmap_dispose(map);
+        libxl_bitmap_init(map);
+        libxl_bitmap_alloc(CTX, map, max_vcpus);
+        libxl_bitmap_set_none(map);
+
+        switch (d_config->b_info.type) {
+        case LIBXL_DOMAIN_TYPE_HVM:
+            version = libxl__device_model_version_running(gc, domid);
+            assert(version != LIBXL_DEVICE_MODEL_VERSION_UNKNOWN);
+            switch (version) {
+            case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
+                rc = libxl__update_avail_vcpus_qmp(gc, domid,
+                                                   max_vcpus, map);
+                break;
+            case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
+            case LIBXL_DEVICE_MODEL_VERSION_NONE:
+                rc = libxl__update_avail_vcpus_xenstore(gc, domid,
+                                                        max_vcpus, map);
+                break;
+            default:
+                abort();
+            }
+            break;
+        case LIBXL_DOMAIN_TYPE_PV:
+            rc = libxl__update_avail_vcpus_xenstore(gc, domid,
+                                                    max_vcpus, map);
+            break;
+        default:
+            abort();
+        }
+
+        if (rc) {
+            LOG(ERROR, "fail to update available cpu map for domain %d", 
domid);
+            goto out;
+        }
+    }
+
     /* Memory limits:
      *
      * Currently there are three memory limits:
-- 
2.1.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel