----- Original Message -----
> From: "Jianjun Duan" <du...@linux.vnet.ibm.com>
> To: qemu-devel@nongnu.org
> Cc: qemu-...@nongnu.org, du...@linux.vnet.ibm.com, dmi...@daynix.com, "peter
> maydell" <peter.mayd...@linaro.org>,
> kra...@redhat.com, m...@redhat.com, da...@gibson.dropbear.id.au,
> pbonz...@redhat.com, veroniaba...@gmail.com,
> quint...@redhat.com, "amit shah" <amit.s...@redhat.com>, mre...@redhat.com,
> kw...@redhat.com, r...@twiddle.net,
> aurel...@aurel32.net, "leon alrae" <leon.al...@imgtec.com>,
> blauwir...@gmail.com, "mark cave-ayland"
> <mark.cave-ayl...@ilande.co.uk>, mdr...@linux.vnet.ibm.com
> Sent: Tuesday, May 31, 2016 8:02:42 PM
> Subject: [QEMU RFC PATCH v3 4/6] Migration: migrate QTAILQ
>
> 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. In our approach such a structure is tagged
> with VMS_CSTM. We then modified vmstate_save_state and vmstate_load_state
> so that when VMS_CSTM is encountered, put and get from VMStateInfo are
> called respectively. 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 | 22 +++++++++++++
> include/qemu/queue.h | 32 ++++++++++++++++++
> migration/vmstate.c | 79
> +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 133 insertions(+)
>
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index 56a4171..da4ef7f 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -185,6 +185,8 @@ enum VMStateFlags {
> * to determine the number of entries in the array. Only valid in
> * combination with one of VMS_VARRAY*. */
> VMS_MULTIPLY_ELEMENTS = 0x4000,
> + /* For fields which need customized handling, such as QTAILQ in
> queue.h*/
> + VMS_CSTM = 0x8000,
Please call this VMS_LINKED. It can be adapted to other data
structures in qemu/queue.h if there is a need later on.
> };
>
> struct VMStateField {
> @@ -245,6 +247,7 @@ 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)
> @@ -656,6 +659,25 @@ 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_CSTM, \
> + .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 f781aa2..003e368 100644
> --- a/include/qemu/queue.h
> +++ b/include/qemu/queue.h
> @@ -437,3 +437,35 @@ struct {
> \
> (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
>
> #endif /* !QEMU_SYS_QUEUE_H_ */
> +
> +/*
> + * 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)
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index 644ba1f..ff56650 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -5,7 +5,9 @@
> #include "migration/vmstate.h"
> #include "qemu/bitops.h"
> #include "qemu/error-report.h"
> +#include "qemu/queue.h"
> #include "trace.h"
> +#include "migration/qjson.h"
>
> static void vmstate_subsection_save(QEMUFile *f, const VMStateDescription
> *vmsd,
> void *opaque, QJSON *vmdesc);
> @@ -120,6 +122,8 @@ int vmstate_load_state(QEMUFile *f, const
> VMStateDescription *vmsd,
> if (field->flags & VMS_STRUCT) {
> ret = vmstate_load_state(f, field->vmsd, addr,
> field->vmsd->version_id);
> + } else if (field->flags & VMS_CSTM) {
> + ret = field->info->get(f, addr, size, field);
> } else {
> ret = field->info->get(f, addr, size, NULL);
>
> @@ -192,6 +196,8 @@ static const char *vmfield_get_type_name(VMStateField
> *field)
>
> if (field->flags & VMS_STRUCT) {
> type = "struct";
> + } else if (field->flags & VMS_CSTM) {
> + type = "customized";
> } else if (field->info->name) {
> type = field->info->name;
> }
> @@ -326,6 +332,8 @@ void vmstate_save_state(QEMUFile *f, const
> VMStateDescription *vmsd,
> }
> if (field->flags & VMS_STRUCT) {
> vmstate_save_state(f, field->vmsd, addr, vmdesc_loop);
> + } else if (field->flags & VMS_CSTM) {
> + field->info->put(f, addr, size, field, vmdesc_loop);
> } else {
> field->info->put(f, addr, size, NULL, NULL);
> }
> @@ -938,3 +946,74 @@ 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)
> +{
> + bool link;
> + int ret = 0;
> + const VMStateDescription *vmsd = field->vmsd;
> + size_t size = field->size;
> + size_t entry = field->start;
> + int version_id = field->version_id;
> + void *elm;
> +
> + trace_vmstate_load_state(vmsd->name, version_id);
> + if (version_id > vmsd->version_id) {
> + trace_vmstate_load_state_end(vmsd->name, "too new", -EINVAL);
> + return -EINVAL;
> + }
> + if (version_id < vmsd->minimum_version_id) {
> + trace_vmstate_load_state_end(vmsd->name, "too old", -EINVAL);
> + return -EINVAL;
> + }
> +
> + while (true) {
> + vmstate_info_bool.get(f, &link, sizeof(bool), NULL);
You can use qemu_get_byte here, and likewise qemu_put_byte below in
put_qtailq.
> + if (!link) {
> + break;
> + }
> +
> + 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_vmstate_load_state_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)
> +{
> + bool link = true;
> + const VMStateDescription *vmsd = field->vmsd;
> + size_t entry = field->start;
> + void *elm;
> +
> + if (vmdesc) {
> + json_prop_str(vmdesc, "vmsd_name", vmsd->name);
> + json_prop_int(vmdesc, "version", vmsd->version_id);
> + json_start_array(vmdesc, "fields");
You need to store the fields exactly once here, even if there are
0 or >1 elements.
Otherwise looks great now!
Paolo
> + }
> +
> + QTAILQ_RAW_FOREACH(elm, pv, entry) {
> + vmstate_info_bool.put(f, &link, sizeof(bool), NULL, NULL);
> + vmstate_save_state(f, vmsd, elm, vmdesc);
> + }
> + link = false;
> + vmstate_info_bool.put(f, &link, sizeof(bool), NULL, NULL);
> + if (vmdesc) {
> + json_end_array(vmdesc);
> + }
> +}
> +const VMStateInfo vmstate_info_qtailq = {
> + .name = "qtailq",
> + .get = get_qtailq,
> + .put = put_qtailq,
> +};
> --
> 1.9.1
>
>
