On 10/14/2016 03:44 AM, Dr. David Alan Gilbert wrote:
> * 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)
>
Thanks for pointing it out. Since the actual application of this patch
is split off, my test didn't go through this path.
>> + .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?
>
It is intended for QTAILQ of any type. So type is not available.
>> #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.
>
OK.
>> + 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.
>
I know previously you wanted it to be error report. But in the migration
code the same error is always just put into trace (vmastate_load_state).
I just want to be consistent.
Thanks,
Jianjun
>> + 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
>
