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@lab.ntt.co.jp>]

Anthony Liguori wrote:
> On 04/21/2010 12:57 AM, Yoshiaki Tamura wrote:
>> Signed-off-by: Yoshiaki Tamura<tamura.yoshiaki@lab.ntt.co.jp>
>
> 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);
>
>
>
>