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

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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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