[Qemu-devel] [PATCH] savevm: Improve error message for blocked migration

[Qemu-devel] [PATCH] savevm: Improve error message for blocked migration

[Kevin Wolf]

If an internal snapshot can't be saved because migration is blocked
(most commonly probably because of AHCI), we had a really bad error
message:

$ echo -e "savevm foo\nquit" | qemu -M q35 /tmp/test.qcow2 -monitor stdio
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) savevm foo
Error -22 while writing VM
(qemu) quit

This patch converts qemu_savevm_state() to the Error infrastructure so
that a useful error pointing to the problematic device is produced now:

$ echo -e "savevm foo\nquit" | qemu -M q35 /tmp/test.qcow2 -monitor stdio
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) savevm foo
State blocked by non-migratable device '0000:00:1f.2/ich9_ahci'
(qemu) quit

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 savevm.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/savevm.c b/savevm.c
index 8040766..1d08165 100644
--- a/savevm.c
+++ b/savevm.c
@@ -821,7 +821,7 @@ void qemu_savevm_state_cancel(void)
     }
 }
 
-static int qemu_savevm_state(QEMUFile *f)
+static int qemu_savevm_state(QEMUFile *f, Error **errp)
 {
     int ret;
     MigrationParams params = {
@@ -829,7 +829,7 @@ static int qemu_savevm_state(QEMUFile *f)
         .shared = 0
     };
 
-    if (qemu_savevm_state_blocked(NULL)) {
+    if (qemu_savevm_state_blocked(errp)) {
         return -EINVAL;
     }
 
@@ -850,6 +850,7 @@ static int qemu_savevm_state(QEMUFile *f)
     }
     if (ret != 0) {
         qemu_savevm_state_cancel();
+        error_setg_errno(errp, -ret, "Error while writing VM state");
     }
     return ret;
 }
@@ -1102,6 +1103,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
     qemu_timeval tv;
     struct tm tm;
     const char *name = qdict_get_try_str(qdict, "name");
+    Error *local_err = NULL;
 
     /* Verify if there is a device that doesn't support snapshots and is writable */
     bs = NULL;
@@ -1160,11 +1162,12 @@ void do_savevm(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "Could not open VM state file\n");
         goto the_end;
     }
-    ret = qemu_savevm_state(f);
+    ret = qemu_savevm_state(f, &local_err);
     vm_state_size = qemu_ftell(f);
     qemu_fclose(f);
     if (ret < 0) {
-        monitor_printf(mon, "Error %d while writing VM\n", ret);
+        monitor_printf(mon, "%s\n", error_get_pretty(local_err));
+        error_free(local_err);
         goto the_end;
     }
 
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH] savevm: Improve error message for blocked migration

[Eric Blake]

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On 02/10/2015 06:25 AM, Kevin Wolf wrote:
> If an internal snapshot can't be saved because migration is blocked
> (most commonly probably because of AHCI), we had a really bad error
> message:
> 
> $ echo -e "savevm foo\nquit" | qemu -M q35 /tmp/test.qcow2 -monitor stdio

You know, 'echo -e' is non-portable (even in bash; you can change shopt
so that it outputs a literal "-e" instead of turning on \
interpretation); it's worth getting used to using 'printf' for
portability.  But that doesn't affect your commit.

> QEMU 2.2.50 monitor - type 'help' for more information
> (qemu) savevm foo
> Error -22 while writing VM
> (qemu) quit
> 
> This patch converts qemu_savevm_state() to the Error infrastructure so
> that a useful error pointing to the problematic device is produced now:
> 
> $ echo -e "savevm foo\nquit" | qemu -M q35 /tmp/test.qcow2 -monitor stdio
> QEMU 2.2.50 monitor - type 'help' for more information
> (qemu) savevm foo
> State blocked by non-migratable device '0000:00:1f.2/ich9_ahci'
> (qemu) quit
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  savevm.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH] savevm: Improve error message for blocked migration

[Stefan Hajnoczi]

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On Tue, Feb 10, 2015 at 02:25:02PM +0100, Kevin Wolf wrote:
> If an internal snapshot can't be saved because migration is blocked
> (most commonly probably because of AHCI), we had a really bad error
> message:
> 
> $ echo -e "savevm foo\nquit" | qemu -M q35 /tmp/test.qcow2 -monitor stdio
> QEMU 2.2.50 monitor - type 'help' for more information
> (qemu) savevm foo
> Error -22 while writing VM
> (qemu) quit
> 
> This patch converts qemu_savevm_state() to the Error infrastructure so
> that a useful error pointing to the problematic device is produced now:
> 
> $ echo -e "savevm foo\nquit" | qemu -M q35 /tmp/test.qcow2 -monitor stdio
> QEMU 2.2.50 monitor - type 'help' for more information
> (qemu) savevm foo
> State blocked by non-migratable device '0000:00:1f.2/ich9_ahci'
> (qemu) quit
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  savevm.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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