Re: [Qemu-devel] [PATCH v2 33/41] postcopy: introduce -postcopy and -postcopy-flags option

[Juan Quintela <quintela@redhat.com>]

Isaku Yamahata <yamahata@valinux.co.jp> wrote:
> This patch prepares for postcopy livemigration.
> It introduces -postcopy option and its internal flag, migration_postcopy.
> It introduces -postcopy-flags for chaging the behavior of incoming postcopy
> mainly for benchmark/debug.

Why do we need postcopy flag?  -incoming should be enough to detect that
we are doing postcopy.

    QLIST_HEAD(, LoadStateEntry) loadvm_handlers =
        QLIST_HEAD_INITIALIZER(loadvm_handlers);
    LoadStateEntry *le, *new_le;
    uint8_t section_type;
    unsigned int v;
    int ret;

    if (qemu_savevm_state_blocked(NULL)) {
        return -EINVAL;
    }

    v = qemu_get_be32(f);
    if (v != QEMU_VM_FILE_MAGIC)
        return -EINVAL;

    v = qemu_get_be32(f);
    if (v == QEMU_VM_FILE_VERSION_COMPAT) {
        fprintf(stderr, "SaveVM v2 format is obsolete and don't work anymore\n");
        return -ENOTSUP;
    }
    if (v != QEMU_VM_FILE_VERSION)
        return -ENOTSUP;

Shouldn't we be able to change some version field here and make the
"recognition of postcopy automatic"?  Having to hack around a new
command line option for each page is not going to be nice.  And about
postcopy flags, if they are for "incoming side", please consider just
sent that flags on the stream as a first field?

Thanks, Juan.