diff options
Diffstat (limited to 'docs/migration.txt')
| -rw-r--r-- | docs/migration.txt | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/docs/migration.txt b/docs/migration.txt index 0719a55002..0e0a1d44da 100644 --- a/docs/migration.txt +++ b/docs/migration.txt @@ -41,7 +41,7 @@ All these four migration protocols use the same infrastructure to save/restore state devices. This infrastructure is shared with the savevm/loadvm functionality. -=== State Live Migration == +=== State Live Migration === This is used for RAM and block devices. It is not yet ported to vmstate. <Fill more information here> @@ -83,7 +83,7 @@ pointer that is passed to all functions. The important functions for us are put_buffer()/get_buffer() that allow to write/read a buffer into the QEMUFile. -=== How to save the state of one device == +=== How to save the state of one device === The state of a device is saved using intermediate buffers. There are some helper functions to assist this saving. @@ -97,7 +97,7 @@ associated with a series of fields saved. The save_state always saves the state as the newer version. But load_state sometimes is able to load state from an older version. - === Legacy way === +=== Legacy way === This way is going to disappear as soon as all current users are ported to VMSTATE. @@ -133,7 +133,7 @@ to interpret that definition to be able to load/save the state. As the state is declared only once, it can't go out of sync in the save/load functions. -An example (from hw/pckbd.c) +An example (from hw/input/pckbd.c) static const VMStateDescription vmstate_kbd = { .name = "pckbd", @@ -158,9 +158,9 @@ We registered this with: Note: talk about how vmstate <-> qdev interact, and what the instance ids mean. You can search for VMSTATE_* macros for lots of types used in QEMU in -hw/hw.h. +include/hw/hw.h. -=== More about versions == +=== More about versions === You can see that there are several version fields: @@ -227,7 +227,7 @@ using a specific functionality, .... It is impossible to create a way to make migration from any version to any other version to work. But we can do better than only allowing -migration from older versions no newer ones. For that fields that are +migration from older versions to newer ones. For that fields that are only needed sometimes, we add the idea of subsections. A subsection is "like" a device vmstate, but with a particularity, it has a Boolean function that tells if that values are needed to be sent or not. If @@ -247,7 +247,8 @@ static bool ide_drive_pio_state_needed(void *opaque) { IDEState *s = opaque; - return (s->status & DRQ_STAT) != 0; + return ((s->status & DRQ_STAT) != 0) + || (s->bus->error_status & BM_STATUS_PIO_RETRY); } const VMStateDescription vmstate_ide_drive_pio_state = { |