On Mon, Jun 12, 2017 at 11:02:34AM +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 <da...@gibson.dropbear.id.au>
> Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com>
> ---
> hw/ppc/spapr.c | 29 +++++++++++++++++++++++++----
> 1 file changed, 25 insertions(+), 4 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 8b541d9..c425499 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1558,13 +1558,19 @@ 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());
> + }
> }
>
>
> @@ -1710,7 +1716,12 @@ 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());
> @@ -1744,7 +1755,12 @@ 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);
> + }
Do you actually need the modifications for _iterate and _complete? I
would have thought you just wouldn't need to send any more of the HPT
stream at all after sending the -1 header.
We should also adjust the downtime estimation logic so we don't allow
for transferring an HPT that isn't there.
> if (!spapr->htab) {
> int rc;
> @@ -1788,6 +1804,11 @@ static int htab_load(QEMUFile *f, void *opaque, int
> version_id)
>
> section_hdr = qemu_get_be32(f);
>
> + if (section_hdr == -1) {
> + spapr_free_hpt(spapr);
> + return 0;
> + }
Strictly speaking we probably shouldn't just return here. We should
wait and see if there is more data in the stream. Any actual content
(i.e. section_hdr == 0 sections) would be an error at this point.
However, a reset to an HPT guest would be represented by a new
non-zero section header, then more data. This isn't urgent, but it
would be nice to fix at some point.
> 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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