Re: [Qemu-devel] [Qemu-ppc] [PATCH 2/2] spapr: Fix stale HTAB during live migration (TCG)

[Alexander Graf <agraf@suse.de>]

On 05.11.14 07:17, Samuel Mendoza-Jonas wrote:
> If a TCG guest reboots during a running migration HTAB entries are not
> marked dirty, and the destination boots with an invalid HTAB.
> 
> When a reboot occurs reset the state of HTAB migration, and explicitly
> inform the destination of invalid entries.
> 
> Signed-off-by: Samuel Mendoza-Jonas <sam.mj@au1.ibm.com>
> ---
>  hw/ppc/spapr.c         | 59 +++++++++++++++++++++++++++++++++++---------------
>  include/hw/ppc/spapr.h |  1 +
>  2 files changed, 42 insertions(+), 18 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 1610c28..9f419e8 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -829,26 +829,30 @@ static void spapr_reset_htab(sPAPREnvironment *spapr)
>  
>      shift = kvmppc_reset_htab(spapr->htab_shift);
>  
> +    pthread_mutex_lock(&spapr->htab_mutex);
>      if (shift > 0) {
>          /* Kernel handles htab, we don't need to allocate one */
>          spapr->htab_shift = shift;
>          kvmppc_kern_htab = true;
>  
>          /* Tell readers to update their file descriptor */
> -        pthread_mutex_lock(&spapr->htab_mutex);
>          if (spapr->htab_fd > 0) {
>              spapr->htab_fd_stale = true;
>          }
> -        pthread_mutex_unlock(&spapr->htab_mutex);
>      } else {
>          if (!spapr->htab) {
>              /* Allocate an htab if we don't yet have one */
>              spapr->htab = qemu_memalign(HTAB_SIZE(spapr), HTAB_SIZE(spapr));
> +        } else {
> +            spapr->htab_mig_full = true;
> +            spapr->htab_first_pass = true;
> +            spapr->htab_save_index = 0;

You could just set the dirty bitmap to "all dirty" here, no? Then you
don't need all the changes belong I presume?

>          }
>  
>          /* And clear it */
>          memset(spapr->htab, 0, HTAB_SIZE(spapr));

... so instead of memset(0)ing it, you could just

  ppc_hash64_store_hpte(env, i, HPTE64_V_HPTE_DIRTY, 0);

the HTAB in a loop.


Alex