From: Alexander Mikhalitsyn <[email protected]> Add VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT{8, 32}_ALLOC, which helps to save/restore a dynamic array of pointers to structures.
Suggested-by: Peter Xu <[email protected]> Signed-off-by: Alexander Mikhalitsyn <[email protected]> v2: - added VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT8_ALLOC v4: - almost completely reworked, new flag VMS_ARRAY_OF_POINTER_ALLOW_NULL was introduced as suggested by Peter --- include/migration/vmstate.h | 77 ++++++++++++++++++++++++++- migration/savevm.c | 26 +++++++++ migration/vmstate-types.c | 102 ++++++++++++++++++++++++++++++++++++ migration/vmstate.c | 54 +++++++++++++++---- 4 files changed, 247 insertions(+), 12 deletions(-) diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h index 5d7dfe70643..70588ed86d7 100644 --- a/include/migration/vmstate.h +++ b/include/migration/vmstate.h @@ -151,7 +151,19 @@ enum VMStateFlags { VMS_VSTRUCT = 0x8000, /* Marker for end of list */ - VMS_END = 0x10000 + VMS_END = 0x10000, + + /* The field is a (fixed-size or variable-size) array of pointers + * (e.g. struct a { uint8_t **b; }) that can contain NULL values. + * This instructs vmstate engine to: + * - Dereference each array entry before using it. + * - Assume that array is initialized with NULLs on load phase + * - Automatically allocate memory for array entries (with size + * specified in (VMStateField).start) on load phase + * - Produce NULL/not-NULL markers in migration stream + * + * Note: Does not imply VMS_ARRAY_OF_POINTER; it needs to be set explicitly. */ + VMS_ARRAY_OF_POINTER_ALLOW_NULL = 0x20000, }; typedef enum { @@ -184,6 +196,7 @@ struct VMStateField { int version_id; int struct_version_id; bool (*field_exists)(void *opaque, int version_id); + const struct VMStateField *real_field; }; struct VMStateDescription { @@ -252,8 +265,10 @@ extern const VMStateInfo vmstate_info_uint64; extern const VMStateInfo vmstate_info_fd; /** Put this in the stream when migrating a null pointer.*/ -#define VMS_NULLPTR_MARKER (0x30U) /* '0' */ +#define VMS_NULLPTR_MARKER (0x30U) /* '0' */ +#define VMS_NOTNULLPTR_MARKER (0x31U) /* '1' */ extern const VMStateInfo vmstate_info_nullptr; +extern const VMStateInfo vmstate_info_maybeptr; extern const VMStateInfo vmstate_info_cpudouble; @@ -265,6 +280,7 @@ extern const VMStateInfo vmstate_info_bitmap; extern const VMStateInfo vmstate_info_qtailq; extern const VMStateInfo vmstate_info_gtree; extern const VMStateInfo vmstate_info_qlist; +extern const VMStateInfo vmstate_info_ptrs_array_entry; #define type_check_2darray(t1,t2,n,m) ((t1(*)[n][m])0 - (t2*)0) /* @@ -547,6 +563,63 @@ extern const VMStateInfo vmstate_info_qlist; .offset = vmstate_offset_array(_s, _f, _type*, _n), \ } +/* + * For migrating a dynamically allocated uint{8,32}-indexed array + * of pointers to structures (with NULL entries and with auto memory allocation). + * + * _type: type of structure pointed to + * _vmsd: VMSD for structure _type (when VMS_STRUCT is set) + * _info: VMStateInfo for _type (when VMS_STRUCT is not set) + * start: size of (_type) pointed to (for auto memory allocation) + */ +#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT8_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \ + .name = (stringify(_field)), \ + .version_id = (_version), \ + .num_offset = vmstate_offset_value(_state, _field_num, uint8_t), \ + .vmsd = &(_vmsd), \ + .start = sizeof(_type), \ + .size = sizeof(_type *), \ + .flags = VMS_POINTER|VMS_VARRAY_UINT8|VMS_ARRAY_OF_POINTER| \ + VMS_ARRAY_OF_POINTER_ALLOW_NULL|VMS_STRUCT, \ + .offset = vmstate_offset_pointer(_state, _field, _type *), \ +} + +#define VMSTATE_VARRAY_OF_POINTER_UINT8_ALLOC(_field, _state, _field_num, _version, _info, _type) { \ + .name = (stringify(_field)), \ + .version_id = (_version), \ + .num_offset = vmstate_offset_value(_state, _field_num, uint8_t), \ + .info = &(_info), \ + .start = sizeof(_type), \ + .size = sizeof(_type *), \ + .flags = VMS_POINTER|VMS_VARRAY_UINT8|VMS_ARRAY_OF_POINTER| \ + VMS_ARRAY_OF_POINTER_ALLOW_NULL, \ + .offset = vmstate_offset_pointer(_state, _field, _type *), \ +} + +#define VMSTATE_VARRAY_OF_POINTER_TO_STRUCT_UINT32_ALLOC(_field, _state, _field_num, _version, _vmsd, _type) { \ + .name = (stringify(_field)), \ + .version_id = (_version), \ + .num_offset = vmstate_offset_value(_state, _field_num, uint32_t), \ + .vmsd = &(_vmsd), \ + .start = sizeof(_type), \ + .size = sizeof(_type *), \ + .flags = VMS_POINTER|VMS_VARRAY_UINT32|VMS_ARRAY_OF_POINTER| \ + VMS_ARRAY_OF_POINTER_ALLOW_NULL|VMS_STRUCT, \ + .offset = vmstate_offset_pointer(_state, _field, _type *), \ +} + +#define VMSTATE_VARRAY_OF_POINTER_UINT32_ALLOC(_field, _state, _field_num, _version, _info, _type) { \ + .name = (stringify(_field)), \ + .version_id = (_version), \ + .num_offset = vmstate_offset_value(_state, _field_num, uint32_t), \ + .info = &(_info), \ + .start = sizeof(_type), \ + .size = sizeof(_type *), \ + .flags = VMS_POINTER|VMS_VARRAY_UINT32|VMS_ARRAY_OF_POINTER| \ + VMS_ARRAY_OF_POINTER_ALLOW_NULL, \ + .offset = vmstate_offset_pointer(_state, _field, _type *), \ +} + #define VMSTATE_VARRAY_OF_POINTER_UINT32(_field, _state, _field_num, _version, _info, _type) { \ .name = (stringify(_field)), \ .version_id = (_version), \ diff --git a/migration/savevm.c b/migration/savevm.c index 197c89e0e65..1ce618d2e66 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -863,6 +863,32 @@ static void vmstate_check(const VMStateDescription *vmsd) if (field) { while (field->name) { + /* + * VMS_ARRAY_OF_POINTER must be used only together + * with one of VMS_(V)ARRAY* flags. + */ + assert(!(field->flags & VMS_ARRAY_OF_POINTER) || + ((field->flags & (VMS_ARRAY | VMS_VARRAY_INT32 | + VMS_VARRAY_UINT16 | VMS_VARRAY_UINT8 | VMS_VARRAY_UINT32)))); + + /* + * When VMS_ARRAY_OF_POINTER_ALLOW_NULL is used, we must: + * 1. have VMS_ARRAY_OF_POINTER set too; + * 2. have ->start field set and it should tell us a size + * of memory chunk we should allocate for every array member. + */ + assert(!(field->flags & VMS_ARRAY_OF_POINTER_ALLOW_NULL) || + (field->flags & VMS_ARRAY_OF_POINTER)); + assert(!(field->flags & VMS_ARRAY_OF_POINTER_ALLOW_NULL) || + field->start); + + /* + * (VMStateField).real_field is only for internal purposes + * and should never be used by any user-defined VMStateField. + * Currently, it is only used by vmsd_create_fake_nullptr_field(). + */ + assert(!field->real_field); + if (field->flags & (VMS_STRUCT | VMS_VSTRUCT)) { /* Recurse to sub structures */ vmstate_check(field->vmsd); diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c index 89cb2114721..8e5431057db 100644 --- a/migration/vmstate-types.c +++ b/migration/vmstate-types.c @@ -377,6 +377,108 @@ const VMStateInfo vmstate_info_nullptr = { .put = put_nullptr, }; +static int get_maybeptr(QEMUFile *f, void *ppv, size_t unused_size, + const VMStateField *field) +{ + Error *local_err = NULL; + Error **errp = &local_err; + int ret = 0; + const VMStateField *real_field = field->real_field; + /* size of structure pointed to by elements of array */ + size_t size = real_field->start; + int marker; + + assert(size); + + if (ppv == NULL) { + error_report("vmstate: get_maybeptr must be called with ppv != NULL"); + return -EINVAL; + } + + /* + * We start from a clean array, all elements must be NULL, unless + * something we haven't prepared for has changed in vmstate_save_state_v(). + * Let's check for this just in case. + */ + if (*(void **)ppv != NULL) { + error_report("vmstate: get_maybeptr must be called with *ppv == NULL"); + return -EINVAL; + } + + marker = qemu_get_byte(f); + assert(marker == VMS_NULLPTR_MARKER || marker == VMS_NOTNULLPTR_MARKER); + + if (marker == VMS_NOTNULLPTR_MARKER) { + void *pv; + + /* allocate memory for structure */ + pv = g_malloc0(size); + + ret = vmstate_load_field(f, pv, size, real_field, errp); + if (ret) { + error_report_err(local_err); + g_free(pv); + return ret; + } + + *(void **)ppv = pv; + } + + return ret; +} + +static int put_maybeptr(QEMUFile *f, void *ppv, size_t unused_size, + const VMStateField *field, JSONWriter *vmdesc) +{ + const VMStateField *real_field = field->real_field; + int ret = 0; + Error *local_err = NULL; + Error **errp = &local_err; + /* size of structure pointed to by elements of array */ + size_t size = real_field->start; + void *pv; + + assert(size); + + /* + * (ppv) is an address of an i-th element of a dynamic array. + * + * (ppv) can not be NULL unless we have some regression/bug in + * vmstate_save_state_v(), because it is result of pointer arithemic like: + * first_elem + size * i. + */ + if (ppv == NULL) { + error_report("vmstate: put_maybeptr must be called with ppv != NULL"); + return -EINVAL; + } + + /* get a pointer to a structure */ + pv = *(void **)ppv; + + if (pv == NULL) { + /* write a mark telling that there was a NULL pointer */ + qemu_put_byte(f, VMS_NULLPTR_MARKER); + return 0; + } + + /* if pv is not NULL, write a marker and save field using vmstate_save_field() */ + qemu_put_byte(f, VMS_NOTNULLPTR_MARKER); + + ret = vmstate_save_field(f, pv, size, real_field, vmdesc, errp); + if (ret) { + error_report_err(local_err); + return ret; + } + + return 0; +} + +const VMStateInfo vmstate_info_maybeptr = { + .name = "maybeptr", + .get = get_maybeptr, + .put = put_maybeptr, +}; + /* 64 bit unsigned int. See that the received value is the same than the one in the field */ diff --git a/migration/vmstate.c b/migration/vmstate.c index 8d192bcaa27..e52046f069d 100644 --- a/migration/vmstate.c +++ b/migration/vmstate.c @@ -71,10 +71,15 @@ vmsd_create_fake_nullptr_field(const VMStateField *field) /* Do not need "field_exists" check as it always exists (which is null) */ fake->field_exists = NULL; - /* See vmstate_info_nullptr - use 1 byte to represent nullptr */ - fake->size = 1; - fake->info = &vmstate_info_nullptr; - fake->flags = VMS_SINGLE; + if (!(field->flags & VMS_ARRAY_OF_POINTER_ALLOW_NULL)) { + /* See vmstate_info_nullptr - use 1 byte to represent nullptr */ + fake->size = 1; + fake->info = &vmstate_info_nullptr; + fake->flags = VMS_SINGLE; + } else { + fake->real_field = field; + fake->info = &vmstate_info_maybeptr; + } /* All the rest fields shouldn't matter.. */ @@ -212,13 +217,28 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, } for (i = 0; i < n_elems; i++) { void *curr_elem = first_elem + size * i; + bool need_fake_field = false; const VMStateField *inner_field; if (field->flags & VMS_ARRAY_OF_POINTER) { - curr_elem = *(void **)curr_elem; + if (!(field->flags & VMS_ARRAY_OF_POINTER_ALLOW_NULL)) { + assert(curr_elem); + curr_elem = *(void **)curr_elem; + need_fake_field = !curr_elem; + } else { + /* + * We expect array of pointers to be initialized. + * We don't want to overwrite curr_elem with it's + * dereferenced value, because we may need to + * allocate memory (depending on what is in the migration + * stream) and write to it later. + */ + assert(!*(void **)curr_elem); + need_fake_field = true; + } } - if (!curr_elem && size) { + if (need_fake_field && size) { /* * If null pointer found (which should only happen in * an array of pointers), use null placeholder and do @@ -226,6 +246,7 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, */ inner_field = vmsd_create_fake_nullptr_field(field); } else { + assert(curr_elem || !size); inner_field = field; } @@ -507,25 +528,38 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, for (i = 0; i < n_elems; i++) { void *curr_elem = first_elem + size * i; + bool need_fake_field = false; const VMStateField *inner_field; bool is_null; int max_elems = n_elems - i; old_offset = qemu_file_transferred(f); if (field->flags & VMS_ARRAY_OF_POINTER) { - assert(curr_elem); - curr_elem = *(void **)curr_elem; + if (!(field->flags & VMS_ARRAY_OF_POINTER_ALLOW_NULL)) { + assert(curr_elem); + curr_elem = *(void **)curr_elem; + need_fake_field = !curr_elem; + } else { + /* + * We always need a fake field to properly handle + * VMS_ARRAY_OF_POINTER_ALLOW_NULL case, because + * even if pointer is not NULL, we still want to + * write a marker in the migration stream. + */ + need_fake_field = true; + } } - if (!curr_elem && size) { + if (need_fake_field && size) { /* * If null pointer found (which should only happen in * an array of pointers), use null placeholder and do * not follow. */ inner_field = vmsd_create_fake_nullptr_field(field); - is_null = true; + is_null = !curr_elem; } else { + assert(curr_elem || !size); inner_field = field; is_null = false; } -- 2.47.3
