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migration: add capability to bypass the shared memory #2

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Jul 24, 2018
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migration: add capability to bypass the shared memory #2

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14 changes: 14 additions & 0 deletions migration/migration.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1476,6 +1476,20 @@ bool migrate_release_ram(void)
return s->enabled_capabilities[MIGRATION_CAPABILITY_RELEASE_RAM];
}

bool migrate_bypass_shared_memory(void)
{
MigrationState *s;

/* it is not workable with postcopy yet. */
if (migrate_postcopy_ram()) {
return false;
}

s = migrate_get_current();

return s->enabled_capabilities[MIGRATION_CAPABILITY_BYPASS_SHARED_MEMORY];
}

bool migrate_postcopy_ram(void)
{
MigrationState *s;
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1 change: 1 addition & 0 deletions migration/migration.h
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Expand Up @@ -178,6 +178,7 @@ MigrationState *migrate_get_current(void);

bool migrate_postcopy(void);

bool migrate_bypass_shared_memory(void);
bool migrate_release_ram(void);
bool migrate_postcopy_ram(void);
bool migrate_zero_blocks(void);
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27 changes: 18 additions & 9 deletions migration/ram.c
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Expand Up @@ -772,6 +772,11 @@ unsigned long migration_bitmap_find_dirty(RAMState *rs, RAMBlock *rb,
unsigned long *bitmap = rb->bmap;
unsigned long next;

/* when this ramblock is requested bypassing */
if (!bitmap) {
return size;
}

if (rs->ram_bulk_stage && start > 0) {
next = start + 1;
} else {
Expand Down Expand Up @@ -842,7 +847,9 @@ static void migration_bitmap_sync(RAMState *rs)
qemu_mutex_lock(&rs->bitmap_mutex);
rcu_read_lock();
RAMBLOCK_FOREACH(block) {
migration_bitmap_sync_range(rs, block, 0, block->used_length);
if (!migrate_bypass_shared_memory() || !qemu_ram_is_shared(block)) {
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I though migrate_bypass_shared_memory was enough

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Even when migrate_bypass_shared_memory is set, ram can be set private instead of being shared. The only case we can skip syncing is migrate_bypass_shared_memory && ram_is_shared.

migration_bitmap_sync_range(rs, block, 0, block->used_length);
}
}
rcu_read_unlock();
qemu_mutex_unlock(&rs->bitmap_mutex);
Expand Down Expand Up @@ -2123,28 +2130,30 @@ static int ram_state_init(RAMState **rsp)
qemu_mutex_init(&(*rsp)->src_page_req_mutex);
QSIMPLEQ_INIT(&(*rsp)->src_page_requests);

/*
* Count the total number of pages used by ram blocks not including any
* gaps due to alignment or unplugs.
*/
(*rsp)->migration_dirty_pages = ram_bytes_total() >> TARGET_PAGE_BITS;

ram_state_reset(*rsp);

return 0;
}

static void ram_list_init_bitmaps(void)
static void ram_list_init_bitmaps(RAMState *rs)
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check if rs is NULL

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If that is possible, the original code would panic at https://github.com/kata-containers/qemu/pull/2/files#diff-7a5fd992f4559f6907ed9fd0a89cd159R839

{
RAMBlock *block;
unsigned long pages;

/* Skip setting bitmap if there is no RAM */
if (ram_bytes_total()) {
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
if (migrate_bypass_shared_memory() && qemu_ram_is_shared(block)) {
continue;
}
pages = block->max_length >> TARGET_PAGE_BITS;
block->bmap = bitmap_new(pages);
bitmap_set(block->bmap, 0, pages);
/*
* Count the total number of pages used by ram blocks not
* including any gaps due to alignment or unplugs.
*/
rs->migration_dirty_pages += pages;
if (migrate_postcopy_ram()) {
block->unsentmap = bitmap_new(pages);
bitmap_set(block->unsentmap, 0, pages);
Expand All @@ -2160,7 +2169,7 @@ static void ram_init_bitmaps(RAMState *rs)
qemu_mutex_lock_ramlist();
rcu_read_lock();

ram_list_init_bitmaps();
ram_list_init_bitmaps(rs);
memory_global_dirty_log_start();
migration_bitmap_sync(rs);

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8 changes: 7 additions & 1 deletion qapi/migration.json
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Expand Up @@ -352,12 +352,17 @@
#
# @x-multifd: Use more than one fd for migration (since 2.11)
#
# @bypass-shared-memory: the shared memory region will be bypassed on migration.
# This feature allows the memory region to be reused by new qemu(s)
# or be migrated separately. (since 2.12)
#
# Since: 1.2
##
{ 'enum': 'MigrationCapability',
'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',
'block', 'return-path', 'pause-before-switchover', 'x-multifd' ] }
'block', 'return-path', 'pause-before-switchover', 'x-multifd',
'bypass-shared-memory'] }

##
# @MigrationCapabilityStatus:
Expand Down Expand Up @@ -412,6 +417,7 @@
# {"state": true, "capability": "events"},
# {"state": false, "capability": "postcopy-ram"},
# {"state": false, "capability": "x-colo"}
# {"state": false, "capability": "bypass-shared-memory"}
# ]}
#
##
Expand Down