Re: [Qemu-devel] [PATCH v5 1/2] spapr: Add a "no HPT" encoding to HTAB migration stream

[David Gibson]

On Wed, Jun 07, 2017 at 01:24:52PM +0530, Bharata B Rao wrote:
> Add a "no HPT" encoding (using value -1) to the HTAB migration
> stream (in the place of HPT size) when the guest doesn't allocate HPT.
> This will help the target side to match target HPT with the source HPT
> and thus enable successful migration.
> 
> Suggested-by: David Gibson <address@hidden>
> Signed-off-by: Bharata B Rao <address@hidden>

As dicussed in the thread on the previous version, I still think you
can use section_hdr == 0 as the no-HPT encoding (matching htab_shift
== 0.

> ---
>  hw/ppc/spapr.c | 28 ++++++++++++++++++++++++----
>  1 file changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 86e6228..df27c5c 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1557,13 +1557,19 @@ static int htab_save_setup(QEMUFile *f, void *opaque)
>      sPAPRMachineState *spapr = opaque;
>  
>      /* "Iteration" header */
> -    qemu_put_be32(f, spapr->htab_shift);
> +    if (!spapr->htab_shift) {
> +        qemu_put_be32(f, -1);
> +    } else {
> +        qemu_put_be32(f, spapr->htab_shift);
> +    }
>  
>      if (spapr->htab) {
>          spapr->htab_save_index = 0;
>          spapr->htab_first_pass = true;
>      } else {
> -        assert(kvm_enabled());
> +        if (spapr->htab_shift) {
> +            assert(kvm_enabled());
> +        }
>      }
>  
>  
> @@ -1709,7 +1715,12 @@ static int htab_save_iterate(QEMUFile *f, void *opaque)
>      int rc = 0;
>  
>      /* Iteration header */
> -    qemu_put_be32(f, 0);
> +    if (!spapr->htab_shift) {
> +        qemu_put_be32(f, -1);
> +        return 0;
> +    } else {
> +        qemu_put_be32(f, 0);
> +    }
>  
>      if (!spapr->htab) {
>          assert(kvm_enabled());
> @@ -1743,7 +1754,12 @@ static int htab_save_complete(QEMUFile *f, void 
> *opaque)
>      int fd;
>  
>      /* Iteration header */
> -    qemu_put_be32(f, 0);
> +    if (!spapr->htab_shift) {
> +        qemu_put_be32(f, -1);
> +        return 0;
> +    } else {
> +        qemu_put_be32(f, 0);
> +    }
>  
>      if (!spapr->htab) {
>          int rc;
> @@ -1787,6 +1803,10 @@ static int htab_load(QEMUFile *f, void *opaque, int 
> version_id)
>  
>      section_hdr = qemu_get_be32(f);
>  
> +    if (section_hdr == -1) {

You should free the existing HPT (if any) here.

> +        return 0;
> +    }
> +
>      if (section_hdr) {
>          Error *local_err = NULL;
>  

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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