[libvirt] [PATCH 6/6] restore correctly the state of the VM upon migration

[Daniel Veillard]

On Thu, Oct 01, 2009 at 08:18:33PM +0200, Paolo Bonzini wrote:
> In order to correctly pass the paused/unpaused state on the remote side,
> we use the newly introduced return code of qemudDomainMigratePerform.
> 
> The return code does not need to be public (it is internal to the QEMU
> driver).  A return code of 0 specifies the old behavior.
> 
> * src/qemu/qemu_driver.c (qemudDomainMigratePerform): Check if
> the machine will have to be resumed on the destination side,
> pass a return value to indicate this.
> (qemudDomainMigrateFinish2): Conditionalize resumption on
> the return code from qemudDomainMigratePerform.
> * src/qemu/qemu_driver.h (qemuDomainMigratePerformResult): New enum.
> ---
>  src/qemu/qemu_driver.c |   14 ++++++++++----
>  src/qemu/qemu_driver.h |    6 ++++++
>  2 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index d2429de..5811ba2 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -37,6 +37,7 @@
>  #include <errno.h>
>  #include <sys/utsname.h>
>  #include <sys/stat.h>
> +#include <assert.h>
>  #include <fcntl.h>
>  #include <signal.h>
>  #include <paths.h>
> @@ -5969,7 +5970,9 @@ cleanup:
>      return ret;
>  }
>  
> -/* Perform is the second step, and it runs on the source host. */
> +/* Perform is the second step, and it runs on the source host.  It
> +   returns a combination of actions that should (or should not) be
> +   done by MigrateFinish2, currently QEMU_MIGRATE_NO_RESUME.  */
>  static int
>  qemudDomainMigratePerform (virDomainPtr dom,
>                             const char *cookie ATTRIBUTE_UNUSED,
> @@ -5983,7 +5986,7 @@ qemudDomainMigratePerform (virDomainPtr dom,
>      virDomainObjPtr vm;
>      virDomainEventPtr event = NULL;
>      int ret = -1;
> -    int paused = 0;
> +    int paused = 0, need_resume = 0;
>      int status;
>      xmlURIPtr uribits = NULL;
>      unsigned long long transferred, remaining, total;
> @@ -6004,6 +6007,7 @@ qemudDomainMigratePerform (virDomainPtr dom,
>          goto cleanup;
>      }
>  
> +    need_resume = (vm->state == VIR_DOMAIN_RUNNING);
>      if (!(flags & VIR_MIGRATE_LIVE)) {
>          /* Pause domain for non-live migration */
>          if (qemuMonitorStopCPUs(vm) < 0)
> @@ -6072,7 +6076,7 @@ qemudDomainMigratePerform (virDomainPtr dom,
>          virDomainRemoveInactive(&driver->domains, vm);
>          vm = NULL;
>      }
> -    ret = 0;
> +    ret = need_resume ? 0 : QEMU_MIGRATE_NO_RESUME;
>  
>  cleanup:
>      if (paused) {
> @@ -6131,7 +6135,9 @@ qemudDomainMigrateFinish2 (virConnectPtr dconn,
>      if (retcode >= 0) {
>          dom = virGetDomain (dconn, vm->def->name, vm->def->uuid);
>  
> -        if (!(flags & VIR_MIGRATE_PAUSED)) {
> +        assert (vm->state == VIR_DOMAIN_PAUSED);

 NACK ! an error in migration should not result in a dead daemon
assert/exit forbidden even in error handling paths.

> +        if (!(retcode & QEMU_MIGRATE_NO_RESUME)
> +            && !(flags & VIR_MIGRATE_PAUSED)) {
>              /* run 'cont' on the destination, which allows migration on qemu
>               * >= 0.10.6 to work properly.  This isn't strictly necessary on
>               * older qemu's, but it also doesn't hurt anything there
> diff --git a/src/qemu/qemu_driver.h b/src/qemu/qemu_driver.h
> index 17b184f..74ec089 100644
> --- a/src/qemu/qemu_driver.h
> +++ b/src/qemu/qemu_driver.h
> @@ -47,6 +47,12 @@
>  #  define KVM_CAP_NR_VCPUS 9       /* returns max vcpus per vm */
>  #endif
>  
> +/* Flags passed from virDomainMigratePerform to virDomainMigrateFinish.  */
> +
> +typedef enum {
> +  QEMU_MIGRATE_NO_RESUME   = 1  /* destination domain should stay paused */
> +} qemuDomainMigratePerformResult;
> +
>  int qemuRegister(void);
>  
>  #endif /* QEMUD_DRIVER_H */
> -- 
> 1.6.2.5
> 
> --
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-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel at veillard.com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/