tools/libxl: Infrastructure to convert a legacy stream

Provide a thin wrapper around exec()ing the python conversion utility,
and a stub implementation for cases where conversion is not wanted
(i.e. not x86).

One complication is that the caller of this interface needs to assume
ownership of the output fd, to prevent it being closed while still in
use in a datacopier.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
v4: Formatting tweaks, description of the width field.
v3: Trimmed down massively from v2, provide libxl_no_convert_callout.c

diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
index c71c5fe7e9fede926a2be69e3d6c591263832ef4..68fe1c1e4ec5b501378b66e05e9de6d65a35407b 100644 (file)
--- a/tools/libxl/Makefile
+++ b/tools/libxl/Makefile
@@ -56,6 +56,12 @@ else
 LIBXL_OBJS-y += libxl_nonetbuffer.o
 endif
 
+ifeq ($(CONFIG_X86),y)
+LIBXL_OBJS-y += libxl_convert_callout.o
+else
+LIBXL_OBJS-y += libxl_no_convert_callout.o
+endif
+
 LIBXL_OBJS-y += libxl_remus_device.o libxl_remus_disk_drbd.o
 
 LIBXL_OBJS-$(CONFIG_X86) += libxl_cpuid.o libxl_x86.o libxl_psr.o

diff --git a/tools/libxl/libxl_convert_callout.c b/tools/libxl/libxl_convert_callout.c
new file mode 100644 (file)
index 0000000..65b4df9
--- /dev/null
+++ b/tools/libxl/libxl_convert_callout.c
@@ -0,0 +1,171 @@
+/*
+ * Copyright (C) 2014      Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include "libxl_osdeps.h"
+
+#include "libxl_internal.h"
+
+/*
+ * Infrastructure for converting a legacy migration stream into a
+ * libxl v2 stream.
+ *
+ * This is done by fork()ing the python conversion script, which takes
+ * in a legacy stream, and puts out a suitably-formatted v2 stream.
+ */
+
+static void helper_exited(libxl__egc *egc, libxl__ev_child *ch,
+                          pid_t pid, int status);
+static void helper_stop(libxl__egc *egc, libxl__ao_abortable *abrt, int rc);
+static void helper_done(libxl__egc *egc,
+                        libxl__conversion_helper_state *chs);
+
+/*----- Entrypoints -----*/
+
+void libxl__conversion_helper_init(libxl__conversion_helper_state *chs)
+{
+    chs->v2_carefd = NULL;
+    chs->rc = 0;
+    libxl__ao_abortable_init(&chs->abrt);
+    libxl__ev_child_init(&chs->child);
+}
+
+int libxl__convert_legacy_stream(libxl__egc *egc,
+                                 libxl__conversion_helper_state *chs)
+{
+    STATE_AO_GC(chs->ao);
+    libxl__carefd *child_in = NULL, *child_out = NULL;
+    int rc = 0;
+
+    chs->abrt.ao = chs->ao;
+    chs->abrt.callback = helper_stop;
+    rc = libxl__ao_abortable_register(&chs->abrt);
+    if (rc) goto err;
+
+    libxl__carefd_begin();
+    int fds[2];
+    if (libxl_pipe(CTX, fds)) {
+        rc = ERROR_FAIL;
+        libxl__carefd_unlock();
+        goto err;
+    }
+    child_out = libxl__carefd_record(CTX, fds[0]);
+    child_in  = libxl__carefd_record(CTX, fds[1]);
+    libxl__carefd_unlock();
+
+    pid_t pid = libxl__ev_child_fork(gc, &chs->child, helper_exited);
+    if (!pid) {
+        char * const args[] =
+        {
+            getenv("LIBXL_CONVERT_HELPER") ?:
+                LIBEXEC_BIN "/convert-legacy-stream",
+            "--in",     GCSPRINTF("%d", chs->legacy_fd),
+            "--out",    GCSPRINTF("%d", fds[1]),
+            /*
+             * The width calculation is an assumption for the common
+             * case.  The conversion script needs to know the width of
+             * the toolstack which saved the legacy stream.
+             *
+             * In the overwhelming majority of cases, the width of the
+             * saving toolstack will be the same as our current
+             * width.  To avoid extending the libxl API with a
+             * parameter intended to disappear shortly, this option
+             * has not been exposed to the caller.
+             *
+             * If more complicated conversion is required, the
+             * conversion script can be instantiated manually, which
+             * will bypass all of this conversion logic.
+             */
+            "--width",  sizeof(unsigned long) == 8 ? "64" : "32",
+
+            "--guest",  chs->hvm ? "hvm" : "pv",
+            "--format", "libxl",
+            /* "--verbose", */
+            NULL,
+        };
+
+        libxl_fd_set_cloexec(CTX, chs->legacy_fd, 0);
+        libxl_fd_set_cloexec(CTX, libxl__carefd_fd(child_in), 0);
+
+        libxl__exec(gc,
+                    -1, -1, -1,
+                    args[0], args, NULL);
+    }
+
+    libxl__carefd_close(child_in);
+    chs->v2_carefd = child_out;
+
+    assert(!rc);
+    return rc;
+
+ err:
+    libxl__ao_abortable_deregister(&chs->abrt);
+    assert(rc);
+    return rc;
+}
+
+void libxl__conversion_helper_abort(libxl__egc *egc,
+                                    libxl__conversion_helper_state *chs,
+                                    int rc)
+{
+    STATE_AO_GC(chs->ao);
+    assert(rc);
+
+    if (libxl__conversion_helper_inuse(chs)) {
+
+        if (!chs->rc)
+            chs->rc = rc;
+
+        libxl__kill(gc, chs->child.pid, SIGTERM, "conversion helper");
+    }
+}
+
+/*----- State handling -----*/
+
+static void helper_stop(libxl__egc *egc, libxl__ao_abortable *abrt, int rc)
+{
+    libxl__conversion_helper_state *chs = CONTAINER_OF(abrt, *chs, abrt);
+    STATE_AO_GC(chs->ao);
+
+    libxl__conversion_helper_abort(egc, chs, rc);
+}
+
+static void helper_exited(libxl__egc *egc, libxl__ev_child *ch,
+                          pid_t pid, int status)
+{
+    libxl__conversion_helper_state *chs = CONTAINER_OF(ch, *chs, child);
+    STATE_AO_GC(chs->ao);
+
+    if (status) {
+        libxl_report_child_exitstatus(
+            CTX, chs->rc ? XTL_DEBUG : XTL_ERROR,
+            "conversion helper", pid, status);
+
+        if (!chs->rc)
+            chs->rc = ERROR_FAIL;
+    }
+
+    helper_done(egc, chs);
+}
+
+static void helper_done(libxl__egc *egc,
+                        libxl__conversion_helper_state *chs)
+{
+    STATE_AO_GC(chs->ao);
+
+    assert(!libxl__conversion_helper_inuse(chs));
+
+    libxl__ao_abortable_deregister(&chs->abrt);
+
+    chs->completion_callback(egc, chs, chs->rc);
+}

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 9397d532f6507fe974df8abdc6b09c0def03d758..97755feb72fa4d1247483f170e1022e4b833b964 100644 (file)
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2917,6 +2917,36 @@ _hidden void libxl__remus_devices_commit(libxl__egc *egc,
                                          libxl__remus_devices_state *rds);
 _hidden int libxl__netbuffer_enabled(libxl__gc *gc);
 
+/*----- Legacy conversion helper -----*/
+typedef struct libxl__conversion_helper_state libxl__conversion_helper_state;
+
+struct libxl__conversion_helper_state {
+    /* public */
+    libxl__ao *ao;
+    int legacy_fd;
+    bool hvm;                  /* pv or hvm domain? */
+    libxl__carefd *v2_carefd;  /* Filled by successful call to
+                                * libxl__convert_legacy_stream().  Caller
+                                * assumes ownership of the fd. */
+    void (*completion_callback)(
+        libxl__egc *egc, libxl__conversion_helper_state *chs, int rc);
+    /* private */
+    int rc;
+    libxl__ao_abortable abrt;
+    libxl__ev_child child;
+};
+
+_hidden void libxl__conversion_helper_init
+                    (libxl__conversion_helper_state *chs);
+_hidden int libxl__convert_legacy_stream(libxl__egc *egc,
+                    libxl__conversion_helper_state *chs);
+_hidden void libxl__conversion_helper_abort(libxl__egc *egc,
+                    libxl__conversion_helper_state *chs, int rc);
+static inline bool libxl__conversion_helper_inuse
+                    (const libxl__conversion_helper_state *chs)
+{ return libxl__ev_child_inuse(&chs->child); }
+
+
 /*----- Domain suspend (save) state structure -----*/
 
 typedef struct libxl__domain_suspend_state libxl__domain_suspend_state;

diff --git a/tools/libxl/libxl_no_convert_callout.c b/tools/libxl/libxl_no_convert_callout.c
new file mode 100644 (file)
index 0000000..6ba4d92
--- /dev/null
+++ b/tools/libxl/libxl_no_convert_callout.c
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2015      Citrix Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include "libxl_osdeps.h"
+
+#include "libxl_internal.h"
+
+void libxl__conversion_helper_init(libxl__conversion_helper_state *chs)
+{
+    libxl__ev_child_init(&chs->child);
+}
+
+int libxl__convert_legacy_stream(libxl__egc *egc,
+                                 libxl__conversion_helper_state *chs)
+{
+    return ERROR_FAIL;
+}
+
+void libxl__conversion_helper_abort(libxl__egc *egc,
+                                    libxl__conversion_helper_state *chs,
+                                    int rc)
+{
+    /* no op */
+}