Re: [RFC PATCH 10/20] Introduce skip_header parameter to qemu_loadvm_state() so that it can be called iteratively without reading the header.

[Yoshiaki Tamura <tamura.yoshiaki@xxxxxxxxxxxxx>]

Anthony Liguori wrote:
> On 04/21/2010 12:57 AM, Yoshiaki Tamura wrote:
> > Signed-off-by: Yoshiaki Tamura<tamura.yoshiaki@xxxxxxxxxxxxx>
>
> I think the more appropriate thing to do is have
> qemu_savevm_state_complete() not write QEMU_VM_EOF when doing a
> continuous live migration.
>
> You would then want qemu_loadvm_state() to detect real EOF and treat
> that the same as QEMU_VM_EOF (provided it occurred at a section boundary).
>
> Of course, this should be a flag to qemu_loadvm_state() as it's not
> always the right behavior.

Sorry.  I couldn't get your intention.
I would appreciate if you could explain the good points of it.

On the receiver side, we need to switch to ft_transaction mode. If the 
qemu_savevm_state_complete() didn't send QEMU_VM_EOF, qemu_loadvm_state() won't 
get out of the loop, and therefore it can switch to ft_transaction mode.

Please let me know if I were misunderstanding.

> Regards,
>
> Anthony Liguori
>
> > ---
> > migration-exec.c | 2 +-
> > migration-fd.c | 2 +-
> > migration-tcp.c | 2 +-
> > migration-unix.c | 2 +-
> > savevm.c | 25 ++++++++++++++-----------
> > sysemu.h | 2 +-
> > 6 files changed, 19 insertions(+), 16 deletions(-)
> >
> > diff --git a/migration-exec.c b/migration-exec.c
> > index 3edc026..5839a6d 100644
> > --- a/migration-exec.c
> > +++ b/migration-exec.c
> > @@ -113,7 +113,7 @@ static void exec_accept_incoming_migration(void
> > *opaque)
> > QEMUFile *f = opaque;
> > int ret;
> >
> > - ret = qemu_loadvm_state(f);
> > + ret = qemu_loadvm_state(f, 0);
> > if (ret< 0) {
> > fprintf(stderr, "load of migration failed\n");
> > goto err;
> > diff --git a/migration-fd.c b/migration-fd.c
> > index 0cc74ad..0e97ed0 100644
> > --- a/migration-fd.c
> > +++ b/migration-fd.c
> > @@ -106,7 +106,7 @@ static void fd_accept_incoming_migration(void
> > *opaque)
> > QEMUFile *f = opaque;
> > int ret;
> >
> > - ret = qemu_loadvm_state(f);
> > + ret = qemu_loadvm_state(f, 0);
> > if (ret< 0) {
> > fprintf(stderr, "load of migration failed\n");
> > goto err;
> > diff --git a/migration-tcp.c b/migration-tcp.c
> > index 56e1a3b..94a1a03 100644
> > --- a/migration-tcp.c
> > +++ b/migration-tcp.c
> > @@ -182,7 +182,7 @@ static void tcp_accept_incoming_migration(void
> > *opaque)
> > goto out;
> > }
> >
> > - ret = qemu_loadvm_state(f);
> > + ret = qemu_loadvm_state(f, 0);
> > if (ret< 0) {
> > fprintf(stderr, "load of migration failed\n");
> > goto out_fopen;
> > diff --git a/migration-unix.c b/migration-unix.c
> > index b7aab38..dd99a73 100644
> > --- a/migration-unix.c
> > +++ b/migration-unix.c
> > @@ -168,7 +168,7 @@ static void unix_accept_incoming_migration(void
> > *opaque)
> > goto out;
> > }
> >
> > - ret = qemu_loadvm_state(f);
> > + ret = qemu_loadvm_state(f, 0);
> > if (ret< 0) {
> > fprintf(stderr, "load of migration failed\n");
> > goto out_fopen;
> > diff --git a/savevm.c b/savevm.c
> > index 22d928c..a401b27 100644
> > --- a/savevm.c
> > +++ b/savevm.c
> > @@ -1554,7 +1554,7 @@ typedef struct LoadStateEntry {
> > int version_id;
> > } LoadStateEntry;
> >
> > -int qemu_loadvm_state(QEMUFile *f)
> > +int qemu_loadvm_state(QEMUFile *f, int skip_header)
> > {
> > QLIST_HEAD(, LoadStateEntry) loadvm_handlers =
> > QLIST_HEAD_INITIALIZER(loadvm_handlers);
> > @@ -1563,17 +1563,20 @@ int qemu_loadvm_state(QEMUFile *f)
> > unsigned int v;
> > int ret;
> >
> > - v = qemu_get_be32(f);
> > - if (v != QEMU_VM_FILE_MAGIC)
> > - return -EINVAL;
> > + if (!skip_header) {
> > + 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 v3 format is obsolete and don't work
> > anymore\n");
> > + return -ENOTSUP;
> > + }
> > + if (v != QEMU_VM_FILE_VERSION)
> > + return -ENOTSUP;
> >
> > - 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;
> >
> > while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
> > uint32_t instance_id, version_id, section_id;
> > @@ -1898,7 +1901,7 @@ int load_vmstate(Monitor *mon, const char *name)
> > monitor_printf(mon, "Could not open VM state file\n");
> > return -EINVAL;
> > }
> > - ret = qemu_loadvm_state(f);
> > + ret = qemu_loadvm_state(f, 0);
> > qemu_fclose(f);
> > if (ret< 0) {
> > monitor_printf(mon, "Error %d while loading VM state\n", ret);
> > diff --git a/sysemu.h b/sysemu.h
> > index 647a468..6c1441f 100644
> > --- a/sysemu.h
> > +++ b/sysemu.h
> > @@ -68,7 +68,7 @@ int qemu_savevm_state_begin(Monitor *mon, QEMUFile
> > *f, int blk_enable,
> > int qemu_savevm_state_iterate(Monitor *mon, QEMUFile *f);
> > int qemu_savevm_state_complete(Monitor *mon, QEMUFile *f);
> > void qemu_savevm_state_cancel(Monitor *mon, QEMUFile *f);
> > -int qemu_loadvm_state(QEMUFile *f);
> > +int qemu_loadvm_state(QEMUFile *f, int skip_header);
> >
> > void qemu_errors_to_file(FILE *fp);
> > void qemu_errors_to_mon(Monitor *mon);


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