[Xen-devel] [PATCH v3] libxl: add libxl_domain_suspend_only to simply suspend a domain, without saving it

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Similar functionality to libxl_domain_suspend(), but do not save domains
state to any file. Only suspend the domain and keep it in suspended
shutdown state (do not destroy it). Such domain can be later woken up
with libxl_domain_resume. The main reason for this functionality is to
suspend the host while some domains are running, potentially holding PCI
devices. This will give a chance to a driver in such a domain to
properly suspend the device.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Marcus of Wetware Labs <marcus@xxxxxxxx>

---
Changes in v3:
 - unbundle functionality to separate libxl_domain_suspend_only function
 - changed title from "libxl: allow libxl_domain_suspend to simply
   suspend a domain, without saving it"
Changes in v2:
 - drop double initialization of dsps fields (libxl__domain_suspend_init
   is called)
 - use LIBXL_SUSPEND_NO_SAVE flag instead of fd=-1
---
 tools/libxl/libxl.h        | 16 ++++++++++++++++
 tools/libxl/libxl_domain.c | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index eca0ea2c50..8936e742eb 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -832,6 +832,14 @@ typedef struct libxl__ctx libxl_ctx;
 #endif
 
 /*
+ * LIBXL_HAVE_DOMAIN_SUSPEND_ONLY
+ *
+ * If this is defined, function libxl_domains_suspend_only() is available.
+ */
+
+#define LIBXL_HAVE_DOMAIN_SUSPEND_ONLY 1
+
+/*
  * LIBXL_HAVE_DEVICE_PCI_SEIZE
  *
  * If this is defined, then the libxl_device_pci struct will contain
@@ -1470,6 +1478,14 @@ int libxl_domain_suspend(libxl_ctx *ctx, uint32_t domid, 
int fd,
 #define LIBXL_SUSPEND_DEBUG 1
 #define LIBXL_SUSPEND_LIVE 2
 
+/*
+ * Only suspend domain, do not save its state to file, do not destroy it.
+ * Suspended domain can be resumed with libxl_domain_resume()
+ */
+int libxl_domain_suspend_only(libxl_ctx *ctx, uint32_t domid,
+                         const libxl_asyncop_how *ao_how)
+                         LIBXL_EXTERNAL_CALLERS_ONLY;
+
 /* @param suspend_cancel [from xenctrl.h:xc_domain_resume( @param fast )]
  *   If this parameter is true, use co-operative resume. The guest
  *   must support this.
diff --git a/tools/libxl/libxl_domain.c b/tools/libxl/libxl_domain.c
index 13b1c73d40..533bcdf240 100644
--- a/tools/libxl/libxl_domain.c
+++ b/tools/libxl/libxl_domain.c
@@ -523,6 +523,40 @@ int libxl_domain_suspend(libxl_ctx *ctx, uint32_t domid, 
int fd, int flags,
     return AO_CREATE_FAIL(rc);
 }
 
+static void domain_suspend_empty_cb(libxl__egc *egc,
+                              libxl__domain_suspend_state *dss, int rc)
+{
+    STATE_AO_GC(dss->ao);
+    libxl__ao_complete(egc,ao,rc);
+}
+
+int libxl_domain_suspend_only(libxl_ctx *ctx, uint32_t domid,
+                              const libxl_asyncop_how *ao_how)
+{
+    AO_CREATE(ctx, domid, ao_how);
+    libxl__domain_suspend_state *dsps;
+    int rc;
+
+    libxl_domain_type type = libxl__domain_type(gc, domid);
+    if (type == LIBXL_DOMAIN_TYPE_INVALID) {
+        rc = ERROR_FAIL;
+        goto out_err;
+    }
+
+    GCNEW(dsps);
+    dsps->ao = ao;
+    dsps->domid = domid;
+    dsps->type = type;
+    rc = libxl__domain_suspend_init(egc, dsps, type);
+    if (rc < 0) goto out_err;
+    dsps->callback_common_done = domain_suspend_empty_cb;
+    libxl__domain_suspend(egc, dsps);
+    return AO_INPROGRESS;
+
+ out_err:
+    return AO_CREATE_FAIL(rc);
+}
+
 int libxl_domain_pause(libxl_ctx *ctx, uint32_t domid)
 {
     int ret;
-- 
2.13.6


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