* Jianjun Duan (du...@linux.vnet.ibm.com) wrote:
> Currently we cannot directly transfer a QTAILQ instance because of the
> limitation in the migration code. Here we introduce an approach to
> transfer such structures. We created VMStateInfo vmstate_info_qtailq
> for QTAILQ. Similar VMStateInfo can be created for other data structures
> such as list.
>
> This approach will be used to transfer pending_events and ccs_list in spapr
> state.
>
> We also create some macros in qemu/queue.h to access a QTAILQ using pointer
> arithmetic. This ensures that we do not depend on the implementation
> details about QTAILQ in the migration code.
>
> Signed-off-by: Jianjun Duan <du...@linux.vnet.ibm.com>
> ---
> include/migration/vmstate.h | 20 +++++++++++++++
> include/qemu/queue.h | 32 ++++++++++++++++++++++++
> migration/trace-events | 4 +++
> migration/vmstate.c | 59
> +++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 115 insertions(+)
>
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index d0e37b5..4dd0aed 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -251,6 +251,7 @@ extern const VMStateInfo vmstate_info_timer;
> extern const VMStateInfo vmstate_info_buffer;
> extern const VMStateInfo vmstate_info_unused_buffer;
> extern const VMStateInfo vmstate_info_bitmap;
> +extern const VMStateInfo vmstate_info_qtailq;
>
> #define type_check_2darray(t1,t2,n,m) ((t1(*)[n][m])0 - (t2*)0)
> #define type_check_array(t1,t2,n) ((t1(*)[n])0 - (t2*)0)
> @@ -662,6 +663,25 @@ extern const VMStateInfo vmstate_info_bitmap;
> .offset = offsetof(_state, _field), \
> }
>
> +/* For QTAILQ that need customized handling
> + * _type: type of QTAILQ element
> + * _next: name of QTAILQ entry field in QTAILQ element
> + * _vmsd: VMSD for QTAILQ element
> + * size: size of QTAILQ element
> + * start: offset of QTAILQ entry in QTAILQ element
> + */
> +#define VMSTATE_QTAILQ_V(_field, _state, _version, _vmsd, _type, _next) \
> +{ \
> + .name = (stringify(_field)), \
> + .version_id = (_version), \
> + .vmsd = &(_vmsd), \
> + .size = sizeof(_type), \
> + .info = &vmstate_info_qtailq, \
> + .flags = VMS_LINKED, \
Hang on - you killed VMS_LINKED off in the previous patch; so this
doesn't work.
(Adding a test to tests/test-vmstate.c would have found that)
> + .offset = offsetof(_state, _field), \
> + .start = offsetof(_type, _next), \
> +}
> +
> /* _f : field name
> _f_n : num of elements field_name
> _n : num of elements
> diff --git a/include/qemu/queue.h b/include/qemu/queue.h
> index 342073f..d672ae0 100644
> --- a/include/qemu/queue.h
> +++ b/include/qemu/queue.h
> @@ -438,4 +438,36 @@ struct {
> \
> #define QTAILQ_PREV(elm, headname, field) \
> (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
>
> +/*
> + * Offsets of layout of a tail queue head.
> + */
> +#define QTAILQ_FIRST_OFFSET 0
> +#define QTAILQ_LAST_OFFSET (sizeof(void *))
> +
> +/*
> + * Offsets of layout of a tail queue element.
> + */
> +#define QTAILQ_NEXT_OFFSET 0
> +#define QTAILQ_PREV_OFFSET (sizeof(void *))
> +
> +/*
> + * Tail queue tranversal using pointer arithmetic.
> + */
> +#define QTAILQ_RAW_FOREACH(elm, head, entry)
> \
> + for ((elm) = *((void **) ((char *) (head) + QTAILQ_FIRST_OFFSET));
> \
> + (elm);
> \
> + (elm) =
> \
> + *((void **) ((char *) (elm) + (entry) +
> QTAILQ_NEXT_OFFSET)))
> +/*
> + * Tail queue insertion using pointer arithmetic.
> + */
> +#define QTAILQ_RAW_INSERT_TAIL(head, elm, entry) do {
> \
> + *((void **) ((char *) (elm) + (entry) + QTAILQ_NEXT_OFFSET)) = NULL;
> \
> + *((void **) ((char *) (elm) + (entry) + QTAILQ_PREV_OFFSET)) =
> \
> + *((void **) ((char *) (head) + QTAILQ_LAST_OFFSET));
> \
> + **((void ***)((char *) (head) + QTAILQ_LAST_OFFSET)) = (elm);
> \
> + *((void **) ((char *) (head) + QTAILQ_LAST_OFFSET)) =
> \
> + (void *) ((char *) (elm) + (entry) + QTAILQ_NEXT_OFFSET);
> \
> +} while (/*CONSTCOND*/0)
I wonder if there's a simpler way to do this; I'm not sure this works, but
something like:
struct QTAILQDummy {
char dummy;
};
QTAILQ_HEAD(QTAILQRawHead, struct QTAILQDummy)
typedef QTAILQ_ENTRY(struct QTAILQDummy) QTAILQRawEntry;
#define QTAILQ_RAW_FOREACH(elm, head, entry) \
for ((elm) = ((struct QTAILQRawHead *)head)->tqh_first) \
(elm); \
(elm) = \
(elm) = ((QTAILQRawEntry *)((char *) (elm) + (entry)))->tqh_next
and then I think elm gets declared as a struct QTAILQDummy.
But it does avoid those FIRST_OFFSET/LAST_OFFSET/NEXT_OFFSET/PREV_OFFSET
calculations.
Would that work?
> #endif /* QEMU_SYS_QUEUE_H */
> diff --git a/migration/trace-events b/migration/trace-events
> index dfee75a..9a6ec59 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -52,6 +52,10 @@ vmstate_n_elems(const char *name, int n_elems) "%s: %d"
> vmstate_subsection_load(const char *parent) "%s"
> vmstate_subsection_load_bad(const char *parent, const char *sub, const char
> *sub2) "%s: %s/%s"
> vmstate_subsection_load_good(const char *parent) "%s"
> +get_qtailq(const char *name, int version_id) "%s v%d"
> +get_qtailq_end(const char *name, const char *reason, int val) "%s %s/%d"
> +put_qtailq(const char *name, int version_id) "%s v%d"
> +put_qtailq_end(const char *name, const char *reason) "%s %s"
>
> # migration/qemu-file.c
> qemu_file_fclose(void) ""
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index e8eff3f..eb68fc6 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -5,6 +5,7 @@
> #include "migration/vmstate.h"
> #include "qemu/bitops.h"
> #include "qemu/error-report.h"
> +#include "qemu/queue.h"
> #include "trace.h"
> #include "migration/qjson.h"
>
> @@ -946,3 +947,61 @@ const VMStateInfo vmstate_info_bitmap = {
> .get = get_bitmap,
> .put = put_bitmap,
> };
> +
> +/*get for QTAILQ */
> +static int get_qtailq(QEMUFile *f, void *pv, size_t unused_size,
> + VMStateField *field)
> +{
> + int ret = 0;
> + const VMStateDescription *vmsd = field->vmsd;
> + size_t size = field->size;
> + size_t entry = field->start;
Please comment these two here; I'd prefer entry_offset or something
as a name to make clear what it is.
> + int version_id = field->version_id;
> + void *elm;
> +
> + trace_get_qtailq(vmsd->name, version_id);
> + if (version_id > vmsd->version_id) {
> + trace_get_qtailq_end(vmsd->name, "too new", -EINVAL);
> + return -EINVAL;
> + }
> + if (version_id < vmsd->minimum_version_id) {
> + trace_get_qtailq_end(vmsd->name, "too old", -EINVAL);
> + return -EINVAL;
> + }
Please make those error_report's - if anything fails migration
I like to see it in the stderr log.
> + while (qemu_get_byte(f)) {
> + elm = g_malloc(size);
> + ret = vmstate_load_state(f, vmsd, elm, version_id);
> + if (ret) {
> + return ret;
> + }
> + QTAILQ_RAW_INSERT_TAIL(pv, elm, entry);
> + }
> +
> + trace_get_qtailq_end(vmsd->name, "end", ret);
> + return ret;
> +}
> +
> +/* put for QTAILQ */
> +static void put_qtailq(QEMUFile *f, void *pv, size_t unused_size,
> + VMStateField *field, QJSON *vmdesc)
> +{
> + const VMStateDescription *vmsd = field->vmsd;
> + size_t entry = field->start;
> + void *elm;
> +
> + trace_put_qtailq(vmsd->name, vmsd->version_id);
> +
> + QTAILQ_RAW_FOREACH(elm, pv, entry) {
> + qemu_put_byte(f, true);
> + vmstate_save_state(f, vmsd, elm, vmdesc);
> + }
> + qemu_put_byte(f, false);
> +
> + trace_put_qtailq_end(vmsd->name, "end");
> +}
> +const VMStateInfo vmstate_info_qtailq = {
> + .name = "qtailq",
> + .get = get_qtailq,
> + .put = put_qtailq,
> +};
> --
> 1.9.1
Dave
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
