Re: [Xen-devel] [PATCH 1/3] libxl: add 2 consoles to stubdoms for save/restore

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 18 Jan 2011, Ian Campbell wrote:
> On Tue, 2011-01-18 at 17:29 +0000, Stefano Stabellini wrote:
> > On Tue, 18 Jan 2011, Ian Campbell wrote:
> > > On Tue, 2011-01-18 at 17:17 +0000, Stefano Stabellini wrote:
> > > > Rename the save file on resume so that it doesn't collide with the
> > > > name of the next save file.  
> > > 
> > > What is the underlying issue here? Why does it matter if a save uses the
> > > same filename as a previous resume? Or is the issue that you can
> > > accidentally resume an image twice?
> > 
> > The issue is that the console backend is going to open both the resume
> > file and the next save file when it starts, so they cannot have the same
> > name.
> 
> Makes sense.
> 
> I think it is worth writing this in the checking comment.
 

Add two "special" PV consoles to stubdoms that are going to be used
to send and receive the qemu-xen save files on save/restore.

Rename the save file on resume so that it doesn't collide with the name
of the next save file (that is opened by the console backend as soon as
it starts so it cannot be the same as the resume state file name).

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>


diff -r 59396addc940 tools/libxl/libxl.c
--- a/tools/libxl/libxl.c       Fri Jan 14 14:26:11 2011 +0000
+++ b/tools/libxl/libxl.c       Tue Jan 18 17:09:56 2011 +0000
@@ -750,7 +750,7 @@ int libxl_primary_console_exec(libxl_ctx
 {
     uint32_t stubdomid = libxl_get_stubdom_id(ctx, domid_vm);
     if (stubdomid)
-        return libxl_console_exec(ctx, stubdomid, 1, LIBXL_CONSTYPE_PV);
+        return libxl_console_exec(ctx, stubdomid, 3, LIBXL_CONSTYPE_PV);
     else {
         if (libxl__domain_is_hvm(ctx, domid_vm))
             return libxl_console_exec(ctx, domid_vm, 0, LIBXL_CONSTYPE_SERIAL);
diff -r 59396addc940 tools/libxl/libxl_create.c
--- a/tools/libxl/libxl_create.c        Fri Jan 14 14:26:11 2011 +0000
+++ b/tools/libxl/libxl_create.c        Tue Jan 18 17:09:56 2011 +0000
@@ -250,8 +250,12 @@ static int domain_restore(libxl_ctx *ctx
 
     dm_info->saved_state = NULL;
     if (info->hvm) {
+        char buf[100];
+        snprintf(buf, sizeof(buf), "/var/lib/xen/qemu-save.%d", domid);
         ret = asprintf(&dm_info->saved_state,
-                       "/var/lib/xen/qemu-save.%d", domid);
+                       "/var/lib/xen/qemu-restore.%d", domid);
+        if (ret >= 0)
+            ret = rename(buf, dm_info->saved_state);
         ret = (ret < 0) ? ERROR_FAIL : 0;
     }
 
diff -r 59396addc940 tools/libxl/libxl_dm.c
--- a/tools/libxl/libxl_dm.c    Fri Jan 14 14:26:11 2011 +0000
+++ b/tools/libxl/libxl_dm.c    Tue Jan 18 17:09:56 2011 +0000
@@ -430,7 +430,7 @@ static int libxl_create_stubdom(libxl_ct
                                 libxl__device_model_starting **starting_r)
 {
     libxl__gc gc = LIBXL_INIT_GC(ctx);
-    int i, num_console = 1, ret;
+    int i, num_console = 3, ret;
     libxl_device_console *console;
     libxl_domain_create_info c_info;
     libxl_domain_build_info b_info;
@@ -533,15 +533,28 @@ retry_transaction:
         console[i].devid = i;
         console[i].consback = LIBXL_CONSBACK_IOEMU;
         console[i].domid = domid;
-        if (!i) {
-            char *filename;
-            char *name = libxl__sprintf(&gc, "qemu-dm-%s", 
libxl_domid_to_name(ctx, info->domid));
-            libxl_create_logfile(ctx, name, &filename);
-            console[i].output = libxl__sprintf(&gc, "file:%s", filename);
-            console[i].build_state = &state;
-            free(filename);
-        } else
-            console[i].output = "pty";
+        switch (i) {
+            case 0:
+                {
+                    char *filename;
+                    char *name = libxl__sprintf(&gc, "qemu-dm-%s", 
libxl_domid_to_name(ctx, info->domid));
+                    libxl_create_logfile(ctx, name, &filename);
+                    console[i].output = libxl__sprintf(&gc, "file:%s", 
filename);
+                    console[i].build_state = &state;
+                    free(filename);
+                }
+                break;
+            case 1:
+                console[i].output = libxl__sprintf(&gc, 
"file:/var/lib/xen/qemu-save.%d", info->domid);
+                break;
+            case 2:
+                if (info->saved_state)
+                    console[i].output = libxl__sprintf(&gc, "filerw:%s", 
info->saved_state);
+                break;
+            default:
+                console[i].output = "pty";
+                break;
+        }
         ret = libxl_device_console_add(ctx, domid, &console[i]);
         if (ret)
             goto out_free;

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