* Jianjun Duan (du...@linux.vnet.ibm.com) wrote:
>
>
> 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.
Yes, but you could add a new entry into test-vmstate.c for this.
> >> + .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.
I think it might be possible to do it generally.
> >> #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.
I should fix those as well to add error_reports !
It's very difficult when we get an error back from a customer with just
a migration failure when the only thing we know is an -EINVAL, so I keep
adding error_report calls.
Dave
> 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
> >
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
