We used to have one vmstate called "nullptr" which is only used to generate
one-byte hint to say one pointer is NULL.
Let's extend its use so that it will generate another byte to say the
pointer is non-NULL.
With that, the name of the info struct (or functions) do not apply anymore.
Update correspondingly.
Update analyze-migration.py to work with the new layout.
No functional change intended yet.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/migration/vmstate.h | 9 +++++++--
migration/vmstate-types.c | 34 ++++++++++++++++------------------
migration/vmstate.c | 25 +++++++++++++------------
scripts/analyze-migration.py | 22 ++++++++++++----------
4 files changed, 48 insertions(+), 42 deletions(-)
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 7396e38531..492069b8d2 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -282,9 +282,14 @@ extern const VMStateInfo vmstate_info_uint32;
extern const VMStateInfo vmstate_info_uint64;
extern const VMStateInfo vmstate_info_fd;
-/** Put this in the stream when migrating a null pointer.*/
+/*
+ * Put this in the stream when migrating a pointer to reflect either a NULL
+ * or valid pointer.
+ */
#define VMS_MARKER_PTR_NULL (0x30U) /* '0' */
-extern const VMStateInfo vmstate_info_nullptr;
+#define VMS_MARKER_PTR_VALID (0x31U) /* '1' */
+
+extern const VMStateInfo vmstate_info_ptr_marker;
extern const VMStateInfo vmstate_info_cpudouble;
diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index 7622cf8f01..b31689fc3c 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -359,36 +359,34 @@ const VMStateInfo vmstate_info_fd = {
.save = save_fd,
};
-static bool load_nullptr(QEMUFile *f, void *pv, size_t size,
- const VMStateField *field, Error **errp)
+static bool load_ptr_marker(QEMUFile *f, void *pv, size_t size,
+ const VMStateField *field, Error **errp)
{
- if (qemu_get_byte(f) == VMS_MARKER_PTR_NULL) {
+ int byte = qemu_get_byte(f);
+
+ if (byte == VMS_MARKER_PTR_NULL || byte == VMS_MARKER_PTR_VALID) {
+ /* TODO: process PTR_VALID case */
return true;
}
- error_setg(errp, "vmstate: load_nullptr expected VMS_NULLPTR_MARKER");
+ error_setg(errp, "%s: unexpected ptr marker: %d", __func__, byte);
return false;
}
-static bool save_nullptr(QEMUFile *f, void *pv, size_t size,
- const VMStateField *field, JSONWriter *vmdesc,
- Error **errp)
+static bool save_ptr_marker(QEMUFile *f, void *pv, size_t size,
+ const VMStateField *field, JSONWriter *vmdesc,
+ Error **errp)
{
- if (pv == NULL) {
- qemu_put_byte(f, VMS_MARKER_PTR_NULL);
- return true;
- }
-
- error_setg(errp, "vmstate: save_nullptr must be called with pv == NULL");
- return false;
+ qemu_put_byte(f, pv ? VMS_MARKER_PTR_VALID : VMS_MARKER_PTR_NULL);
+ return true;
}
-const VMStateInfo vmstate_info_nullptr = {
- .name = "nullptr",
- .load = load_nullptr,
- .save = save_nullptr,
+const VMStateInfo vmstate_info_ptr_marker = {
+ .name = "ptr-marker",
+ .load = load_ptr_marker,
+ .save = save_ptr_marker,
};
/* 64 bit unsigned int. See that the received value is the same than the one
diff --git a/migration/vmstate.c b/migration/vmstate.c
index b274204e66..b333aa1744 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -55,12 +55,12 @@ vmstate_field_exists(const VMStateDescription *vmsd, const VMStateField *field,
}
/*
- * Create a fake nullptr field when there's a NULL pointer detected in the
+ * Create a ptr marker field when there's a NULL pointer detected in the
* array of a VMS_ARRAY_OF_POINTER VMSD field. It's needed because we
* can't dereference the NULL pointer.
*/
static const VMStateField *
-vmsd_create_fake_nullptr_field(const VMStateField *field)
+vmsd_create_ptr_marker_field(const VMStateField *field)
{
VMStateField *fake = g_new0(VMStateField, 1);
@@ -71,12 +71,12 @@ vmsd_create_fake_nullptr_field(const VMStateField *field)
fake->name = field->name;
fake->version_id = field->version_id;
- /* Do not need "field_exists" check as it always exists (which is null) */
+ /* Do not need "field_exists" check as it always exists */
fake->field_exists = NULL;
- /* See vmstate_info_nullptr - use 1 byte to represent nullptr */
+ /* See vmstate_info_ptr_marker - use 1 byte to represent ptr status */
fake->size = 1;
- fake->info = &vmstate_info_nullptr;
+ fake->info = &vmstate_info_ptr_marker;
fake->flags = VMS_SINGLE;
/* All the rest fields shouldn't matter.. */
@@ -278,7 +278,7 @@ bool vmstate_load_vmsd(QEMUFile *f, const VMStateDescription *vmsd,
* an array of pointers), use null placeholder and do
* not follow.
*/
- inner_field = vmsd_create_fake_nullptr_field(field);
+ inner_field = vmsd_create_ptr_marker_field(field);
} else {
inner_field = field;
}
@@ -583,26 +583,27 @@ static bool vmstate_save_vmsd_v(QEMUFile *f, const VMStateDescription *vmsd,
for (i = 0; i < n_elems; i++) {
void *curr_elem = first_elem + size * i;
const VMStateField *inner_field;
- bool is_null;
/* maximum number of elements to compress in the JSON blob */
int max_elems = vmsd_can_compress(field) ? (n_elems - i) : 1;
+ bool use_marker_field, is_null;
if (field->flags & VMS_ARRAY_OF_POINTER) {
assert(curr_elem);
curr_elem = *(void **)curr_elem;
}
- if (!curr_elem && size) {
+ is_null = !curr_elem && size;
+ use_marker_field = is_null;
+
+ if (use_marker_field) {
/*
* 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;
+ inner_field = vmsd_create_ptr_marker_field(field);
} else {
inner_field = field;
- is_null = false;
}
/*
@@ -638,7 +639,7 @@ static bool vmstate_save_vmsd_v(QEMUFile *f, const VMStateDescription *vmsd,
i, max_elems, errp);
/* If we used a fake temp field.. free it now */
- if (is_null) {
+ if (use_marker_field) {
g_clear_pointer((gpointer *)&inner_field, g_free);
}
diff --git a/scripts/analyze-migration.py b/scripts/analyze-migration.py
index e81deab8f9..1771ff781b 100755
--- a/scripts/analyze-migration.py
+++ b/scripts/analyze-migration.py
@@ -469,26 +469,26 @@ def __init__(self, desc, file):
super(VMSDFieldIntLE, self).__init__(desc, file)
self.dtype = '<i%d' % self.size
-class VMSDFieldNull(VMSDFieldGeneric):
+class VMSDFieldPtrMarker(VMSDFieldGeneric):
NULL_PTR_MARKER = b'0'
+ VALID_PTR_MARKER = b'1'
def __init__(self, desc, file):
- super(VMSDFieldNull, self).__init__(desc, file)
+ super(VMSDFieldPtrMarker, self).__init__(desc, file)
def __repr__(self):
- # A NULL pointer is encoded in the stream as a '0' to
- # disambiguate from a mere 0x0 value and avoid consumers
- # trying to follow the NULL pointer. Displaying '0', 0x30 or
- # 0x0 when analyzing the JSON debug stream could become
+ # A NULL / non-NULL pointer may be encoded in the stream as a
+ # '0'/'1' to represent the status of the pointer. Displaying '0',
+ # 0x30 or 0x0 when analyzing the JSON debug stream could become
# confusing, so use an explicit term instead.
- return "nullptr"
+ return "null-ptr" if self.data == self.NULL_PTR_MARKER else "valid-ptr"
def __str__(self):
return self.__repr__()
def read(self):
- super(VMSDFieldNull, self).read()
- assert(self.data == self.NULL_PTR_MARKER)
+ super(VMSDFieldPtrMarker, self).read()
+ assert(self.data in [self.NULL_PTR_MARKER, self.VALID_PTR_MARKER])
return self.data
class VMSDFieldBool(VMSDFieldGeneric):
@@ -642,7 +642,9 @@ def getDict(self):
"bitmap" : VMSDFieldGeneric,
"struct" : VMSDFieldStruct,
"capability": VMSDFieldCap,
- "nullptr": VMSDFieldNull,
+ # Keep the old nullptr for old binaries
+ "nullptr": VMSDFieldPtrMarker,
+ "ptr-marker": VMSDFieldPtrMarker,
"unknown" : VMSDFieldGeneric,
}
--
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