Migration subsections (and ide as example)

v3:
- spell checking documentation
- s/[Qq]emu/QEMU/

v2:
- add documentation
- improve commit messages
- remove debug printf's
- rebase latest qemu

v1:

At the end, here is the migration subsections implementation. As an example I ported the last two ide changes to migration to work with subsections. Notes:

- subsections
I went for qemu_peek_byte() insteadof adding a subsection part in qemu_loadvm_state() due to two reasons:
- it makes mandatory that subsections came after sections (better for error messages)
- it makes post_load() for the section to be run after subsections are loaded. I think that running section post_load() and then subsections can make for some subtle errors.
How does it works?
We have a new array of subsections at the end of each section (it can be NULL). Each subsection is composed of VMStateDescription and a test function. test function checks if subsection is needed or not. if needed, it is just emmited.
On load, we peek to see if after a section is loaded, if there is any subsection at the end, and if so, we search for it on this section subsections.

- ide: 1st revert is not clear because there has been posterior changes that I honored. only change done is that ide_dummy_transfer_stop to transfer_end_table for it to be complete.

- testing. In normal operation this code is not triggered (one of the reason for not wanting to sent it in the 1st place). I used patch attached at the end to trigger it.

Commetnts?

Later, Juan.

index 59341a1..a4e6b82 100644
@@ -421,6 +421,15 @@ static void ide_sector_read(IDEState *s)
         ide_set_irq(s->bus);
         ide_set_sector(s, sector_num + n);
         s->nsector -= n;
+    if ((s->status & DRQ_STAT)) {
+        static int val = 1;
+        if (((val++) == 1000)) {
+            qemu_aio_flush();
+            vm_stop(0);
+            printf("stopped %d ide_ioport_readaaa\n", val);
+        }
+    }
+
     }
 }
 

@@ -2744,6 +2753,14 @@ static int ide_drive_pio_post_load(void *opaque, int version_id)
     s->data_ptr = s->io_buffer + s->cur_io_buffer_offset;
     s->data_end = s->data_ptr + s->cur_io_buffer_len;
 
+    printf("addr %p: status %d\n", s, s->status& DRQ_STAT);
+    printf("\tdata_ptr %p\n", s->data_ptr);
+    printf("\tdata_end %p\n", s->data_end);
+    printf("\tio_buffer %p\n", s->io_buffer);
+    printf("\treq_nb_sectors %d\n", s->req_nb_sectors);
+    printf("\tidx %d\n", transfer_end_table_idx(s->end_transfer_func));
+    printf("\telementary_transfer_size %d\n", s->elementary_transfer_size);
+    printf("\tpacket_transfer_size %d\n", s->packet_transfer_size);
     return 0;
 }
 

@@ -2763,6 +2780,15 @@ static void ide_drive_pio_pre_save(void *opaque)
     } else {
         s->end_transfer_fn_idx = idx;
     }
+
+    printf("addr %p: status %d\n", s, s->status& DRQ_STAT);
+    printf("\tdata_ptr %p\n", s->data_ptr);
+    printf("\tdata_end %p\n", s->data_end);
+    printf("\tio_buffer %p\n", s->io_buffer);
+    printf("\treq_nb_sectors %d\n", s->req_nb_sectors);
+    printf("\tidx %d\n", transfer_end_table_idx(s->end_transfer_func));
+    printf("\telementary_transfer_size %d\n", s->elementary_transfer_size);
+    printf("\tpacket_transfer_size %d\n", s->packet_transfer_size);
 }
 
 static bool ide_drive_pio_state_needed(void *opaque)

Juan Quintela (6):
Revert "ide save/restore pio/atapi cmd transfer fields and io buffer" Revert "ide save/restore current transfer fields"
vmstate: add subsections code
ide: fix migration in the middle of pio operation
ide: fix migration in the middle of a bmdma transfer Initial documentation for migration

 docs/migration.txt |  303 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/hw.h            |    6 +
 hw/ide/core.c      |   72 +++++++++----
 hw/ide/pci.c       |   38 ++++++-
 savevm.c           |   86 +++++++++++++++-
 5 files changed, 477 insertions(+), 28 deletions(-)
 create mode 100644 docs/migration.txt