Re: [libvirt] [PATCH RFC] Add domainSave/Restore to libxl driver

[Markus Groß <gross univention de>]

Am Montag 23 Mai 2011 04:30:12 schrieb Jim Fehlig:
> Jim Fehlig wrote:
> > Markus Groß wrote:
> >   
> >> This patch adds save/restore functionality to the libxl driver.
> >>
> >> It is a v2 of this patch:
> >> https://www.redhat.com/archives/libvir-list/2011-April/msg00338.html
> >>
> >> v2:
> >> * header is now padded and has a version field
> >> * the correct restore function from libxl is used
> >> * only create the restore event once in libxlVmStart
> >>   
> >>     
> >
> > Hi Markus,
> >
> > Finally found time to try your patch.  Thanks for the patience :-).
> >
> >   
> >> However I ran into a reproducible segfault.
> >> Assume you saved a vm with:
> >> # virsh save domU foo.img
> >>   
> >>     
> >
> > I think the problem actually lies in the save function.  The domain does
> > not appear to be cleaned up properly.  From xl's perspective after virsh
> > save domU foo.img
> >
> > xen33: # xl list
> > Name                                        ID   Mem VCPUs      State  
> > Time(s)
> > Domain-0                                  0    2023     8            
> > r-----     330.0
> > (null)                                         11     1         
> > 2             --pssd      27.1
> >
> > The orphaned domain disappears after libvirtd restart.
> 
> I manged to track down this problem, patch posted to xen-devel
> 
> http://lists.xensource.com/archives/html/xen-devel/2011-05/msg01314.html
> 

Great! I attached the current version of the save/restore patch.
It is rebased against the current master.

> 
> >   
> >> If you restore the save image,
> >> destroy the vm and restore it again, a segfault occurs:
> >> # virsh restore foo.img
> >> # virsh destroy domU
> >> # virsh restore foo.img
> >> # segfault
> >>     
> 
> But I still see the segfault, in addition to domain not booting and
> consuming 100% cpu on first restore :-(.  I'll look at these issues next.
> 
> Regards,
> Jim
> 
> 

diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h
index 65110cf..e75e418 100644
--- a/src/libxl/libxl_conf.h
+++ b/src/libxl/libxl_conf.h
@@ -1,5 +1,6 @@
 /*---------------------------------------------------------------------------*/
 /*  Copyright (c) 2011 SUSE LINUX Products GmbH, Nuernberg, Germany.
+ *  Copyright (C) 2011 Univention GmbH.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -17,6 +18,7 @@
  *
  * Authors:
  *     Jim Fehlig <jfehlig novell com>
+ *     Markus Groß <gross univention de>
  */
 /*---------------------------------------------------------------------------*/
 
@@ -81,6 +83,18 @@ struct _libxlDomainObjPrivate {
     int eventHdl;
 };
 
+#define LIBXL_SAVE_MAGIC "libvirt-xml\n \0 \r"
+#define LIBXL_SAVE_VERSION 1
+
+typedef struct _libxlSavefileHeader libxlSavefileHeader;
+typedef libxlSavefileHeader *libxlSavefileHeaderPtr;
+struct _libxlSavefileHeader {
+    char magic[sizeof(LIBXL_SAVE_MAGIC)-1];
+    uint32_t version;
+    uint32_t xmlLen;
+    /* 24 bytes used, pad up to 64 bytes */
+    uint32_t unused[10];
+};
 
 # define libxlError(code, ...)                                     \
     virReportErrorHelper(VIR_FROM_LIBXL, code, __FILE__,           \
diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index b2cc0e8..9bc71fd 100644
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -29,6 +29,7 @@
 #include <sys/utsname.h>
 #include <math.h>
 #include <libxl.h>
+#include <fcntl.h>
 
 #include "internal.h"
 #include "logging.h"
@@ -60,11 +61,10 @@
 
 static libxlDriverPrivatePtr libxl_driver = NULL;
 
-
 /* Function declarations */
 static int
-libxlVmStart(libxlDriverPrivatePtr driver,
-             virDomainObjPtr vm, bool start_paused);
+libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
+             bool start_paused, int restore_fd);
 
 
 /* Function definitions */
@@ -168,7 +168,7 @@ libxlAutostartDomain(void *payload, const void *name ATTRIBUTE_UNUSED,
     virResetLastError();
 
     if (vm->autostart && !virDomainObjIsActive(vm) &&
-        libxlVmStart(driver, vm, false) < 0) {
+        libxlVmStart(driver, vm, false, -1) < 0) {
         err = virGetLastError();
         VIR_ERROR(_("Failed to autostart VM '%s': %s"),
                   vm->def->name,
@@ -369,7 +369,7 @@ static void libxlEventHandler(int watch,
                 break;
             case SHUTDOWN_reboot:
                 libxlVmReap(driver, vm, 0, VIR_DOMAIN_SHUTOFF_SHUTDOWN);
-                libxlVmStart(driver, vm, 0);
+                libxlVmStart(driver, vm, 0, -1);
                 break;
             default:
                 VIR_INFO("Unhandled shutdown_reason %d", info.shutdown_reason);
@@ -535,8 +535,8 @@ libxlFreeMem(libxlDomainObjPrivatePtr priv, libxl_domain_config *d_config)
  * virDomainObjPtr should be locked on invocation
  */
 static int
-libxlVmStart(libxlDriverPrivatePtr driver,
-             virDomainObjPtr vm, bool start_paused)
+libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
+             bool start_paused, int restore_fd)
 {
     libxl_domain_config d_config;
     virDomainDefPtr def = vm->def;
@@ -559,12 +559,23 @@ libxlVmStart(libxlDriverPrivatePtr driver,
         goto error;
     }
 
-    ret = libxl_domain_create_new(&priv->ctx, &d_config,
-                                  NULL, &child_console_pid, &domid);
+    if (restore_fd < 0)
+        ret = libxl_domain_create_new(&priv->ctx, &d_config,
+                                      NULL, &child_console_pid, &domid);
+    else
+        ret = libxl_domain_create_restore(&priv->ctx, &d_config, NULL,
+                                          &child_console_pid, &domid,
+                                          restore_fd);
+
     if (ret) {
-        libxlError(VIR_ERR_INTERNAL_ERROR,
-                   _("libxenlight failed to create new domain '%s'"),
-                   d_config.c_info.name);
+        if (restore_fd < 0)
+            libxlError(VIR_ERR_INTERNAL_ERROR,
+                       _("libxenlight failed to create new domain '%s'"),
+                       d_config.c_info.name);
+        else
+            libxlError(VIR_ERR_INTERNAL_ERROR,
+                       _("libxenlight failed to restore domain '%s'"),
+                       d_config.c_info.name);
         goto error;
     }
 
@@ -597,7 +608,9 @@ libxlVmStart(libxlDriverPrivatePtr driver,
         goto error;
 
     event = virDomainEventNewFromObj(vm, VIR_DOMAIN_EVENT_STARTED,
-                                     VIR_DOMAIN_EVENT_STARTED_BOOTED);
+                                     restore_fd < 0 ?
+                                         VIR_DOMAIN_EVENT_STARTED_BOOTED :
+                                         VIR_DOMAIN_EVENT_STARTED_RESTORED);
     libxlDomainEventQueue(driver, event);
 
     libxl_domain_config_destroy(&d_config);
@@ -1075,7 +1088,8 @@ libxlDomainCreateXML(virConnectPtr conn, const char *xml,
         goto cleanup;
     def = NULL;
 
-    if (libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0) < 0) {
+    if (libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0,
+                     -1) < 0) {
         virDomainRemoveInactive(&driver->domains, vm);
         vm = NULL;
         goto cleanup;
@@ -1627,6 +1641,184 @@ libxlDomainGetState(virDomainPtr dom,
 }
 
 static int
+libxlDomainSave(virDomainPtr dom, const char *to)
+{
+    libxlDriverPrivatePtr driver = dom->conn->privateData;
+    virDomainObjPtr vm;
+    libxlDomainObjPrivatePtr priv;
+    virDomainEventPtr event = NULL;
+    libxlSavefileHeader hdr;
+    char *xml;
+    uint32_t xml_len;
+    int fd;
+    int ret = -1;
+
+    libxlDriverLock(driver);
+    vm = virDomainFindByUUID(&driver->domains, dom->uuid);
+
+    if (!vm) {
+        char uuidstr[VIR_UUID_STRING_BUFLEN];
+        virUUIDFormat(dom->uuid, uuidstr);
+        libxlError(VIR_ERR_NO_DOMAIN,
+                   _("No domain with matching uuid '%s'"), uuidstr);
+        goto cleanup;
+    }
+
+    if (!virDomainObjIsActive(vm)) {
+        libxlError(VIR_ERR_OPERATION_INVALID, "%s", _("Domain is not running"));
+        goto cleanup;
+    }
+
+    priv = vm->privateData;
+
+    if (virDomainObjGetState(vm, NULL) != VIR_DOMAIN_PAUSED) {
+
+        if ((fd = virFileOpenAs(to, O_CREAT|O_TRUNC|O_WRONLY, S_IRUSR|S_IWUSR,
+                                getuid(), getgid(), 0)) < 0) {
+            virReportSystemError(-fd,
+                                 _("Failed to create domain save file '%s'"),
+                                 to);
+            goto cleanup;
+        }
+
+        if ((xml = virDomainDefFormat(vm->def, 0)) == NULL)
+            goto cleanup;
+        xml_len = strlen(xml) + 1;
+
+        memset(&hdr, 0, sizeof(hdr));
+        memcpy(hdr.magic, LIBXL_SAVE_MAGIC, sizeof(hdr.magic));
+        hdr.version = LIBXL_SAVE_VERSION;
+        hdr.xmlLen = xml_len;
+
+        if (safewrite(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) {
+            libxlError(VIR_ERR_OPERATION_FAILED,
+                       _("Failed to write save file header"));
+            goto cleanup;
+        }
+
+        if (safewrite(fd, xml, xml_len) != xml_len) {
+            libxlError(VIR_ERR_OPERATION_FAILED,
+                       _("Failed to write xml description"));
+            goto cleanup;
+        }
+
+        if (libxl_domain_suspend(&priv->ctx, NULL, dom->id, fd) != 0) {
+            libxlError(VIR_ERR_INTERNAL_ERROR,
+                       _("Failed to save domain '%d' with libxenlight"),
+                       dom->id);
+            goto cleanup;
+        }
+
+        event = virDomainEventNewFromObj(vm, VIR_DOMAIN_EVENT_STOPPED,
+                                         VIR_DOMAIN_EVENT_STOPPED_SAVED);
+
+        if (libxlVmReap(driver, vm, 1, VIR_DOMAIN_SHUTOFF_SAVED) != 0) {
+            libxlError(VIR_ERR_INTERNAL_ERROR,
+                       _("Failed to destroy domain '%d'"), dom->id);
+            goto cleanup;
+        }
+
+        if (!vm->persistent) {
+            virDomainRemoveInactive(&driver->domains, vm);
+            vm = NULL;
+        }
+        ret = 0;
+    }
+cleanup:
+    VIR_FREE(xml);
+    if (VIR_CLOSE(fd) < 0)
+        virReportSystemError(errno, "%s", _("cannot close file"));
+    if (vm)
+        virDomainObjUnlock(vm);
+    if (event)
+        libxlDomainEventQueue(driver, event);
+    libxlDriverUnlock(driver);
+    return ret;
+}
+
+static int
+libxlDomainRestore(virConnectPtr conn, const char *from)
+{
+    libxlDriverPrivatePtr driver = conn->privateData;
+    virDomainDefPtr def = NULL;
+    virDomainObjPtr vm = NULL;
+    libxlSavefileHeader hdr;
+    char *xml = NULL;
+    int fd;
+    int ret = -1;
+
+    libxlDriverLock(driver);
+
+    if ((fd = virFileOpenAs(from, O_RDONLY, 0, getuid(), getgid(), 0)) < 0) {
+        libxlError(VIR_ERR_OPERATION_FAILED,
+                   "%s", _("cannot read domain image"));
+        goto cleanup;
+    }
+
+    if (saferead(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) {
+        libxlError(VIR_ERR_OPERATION_FAILED,
+                   "%s", _("failed to read libxl header"));
+        goto cleanup;
+    }
+
+    if (memcmp(hdr.magic, LIBXL_SAVE_MAGIC, sizeof(hdr.magic))) {
+        libxlError(VIR_ERR_INVALID_ARG, "%s", _("image magic is incorrect"));
+        goto cleanup;
+    }
+
+    if (hdr.version > LIBXL_SAVE_VERSION) {
+        libxlError(VIR_ERR_OPERATION_FAILED,
+                   _("image version is not supported (%d > %d)"),
+                   hdr.version, LIBXL_SAVE_VERSION);
+        goto cleanup;
+    }
+
+    if (hdr.xmlLen <= 0) {
+        libxlError(VIR_ERR_OPERATION_FAILED,
+                   _("invalid XML length: %d"), hdr.xmlLen);
+        goto cleanup;
+    }
+
+    if (VIR_ALLOC_N(xml, hdr.xmlLen) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    if (saferead(fd, xml, hdr.xmlLen) != hdr.xmlLen) {
+        libxlError(VIR_ERR_OPERATION_FAILED, "%s", _("failed to read XML"));
+        goto cleanup;
+    }
+
+    if (!(def = virDomainDefParseString(driver->caps, xml,
+                                        VIR_DOMAIN_XML_INACTIVE)))
+        goto cleanup;
+
+    if (virDomainObjIsDuplicate(&driver->domains, def, 1) < 0)
+        goto cleanup;
+
+    if (!(vm = virDomainAssignDef(driver->caps, &driver->domains, def, true)))
+        goto cleanup;
+
+    def = NULL;
+
+    if ((ret = libxlVmStart(driver, vm, false, fd)) < 0 &&
+        !vm->persistent) {
+        virDomainRemoveInactive(&driver->domains, vm);
+        vm = NULL;
+    }
+
+cleanup:
+    VIR_FREE(xml);
+    virDomainDefFree(def);
+    if (VIR_CLOSE(fd) < 0)
+        virReportSystemError(errno, "%s", _("cannot close file"));
+    if (vm)
+        virDomainObjUnlock(vm);
+    libxlDriverUnlock(driver);
+    return ret;
+}
+
+static int
 libxlDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
                          unsigned int flags)
 {
@@ -2096,7 +2288,7 @@ libxlDomainCreateWithFlags(virDomainPtr dom,
         goto cleanup;
     }
 
-    ret = libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0);
+    ret = libxlVmStart(driver, vm, (flags & VIR_DOMAIN_START_PAUSED) != 0, -1);
 
 cleanup:
     if (vm)
@@ -2722,6 +2914,8 @@ static virDriver libxlDriver = {
     .domainSetMemoryFlags = libxlDomainSetMemoryFlags, /* 0.9.0 */
     .domainGetInfo = libxlDomainGetInfo, /* 0.9.0 */
     .domainGetState = libxlDomainGetState, /* 0.9.2 */
+    .domainSave = libxlDomainSave, /* 0.9.2 */
+    .domainRestore = libxlDomainRestore, /* 0.9.2 */
     .domainSetVcpus = libxlDomainSetVcpus, /* 0.9.0 */
     .domainSetVcpusFlags = libxlDomainSetVcpusFlags, /* 0.9.0 */
     .domainGetVcpusFlags = libxlDomainGetVcpusFlags, /* 0.9.0 */