* Cédric Le Goater (c...@kaod.org) wrote:
> On the POWER9 processor, the XIVE interrupt controller can control
> interrupt sources using MMIO to trigger events, to EOI or to turn off
> the sources. Priority management and interrupt acknowledgment is also
> controlled by MMIO in the presenter sub-engine.
>
> These MMIO regions are exposed to guests in QEMU with a set of 'ram
> device' memory mappings, similarly to VFIO, and the VMAs are populated
> dynamically with the appropriate pages using a fault handler.
>
> But, these regions are an issue for migration. We need to discard the
> associated RAMBlocks from the RAM state on the source VM and let the
> destination VM rebuild the memory mappings on the new host in the
> post_load() operation just before resuming the system.
>
> To achieve this goal, the following introduces a new RAMBlock flag
> RAM_MIGRATABLE which is updated in the vmstate_register_ram() and
> vmstate_unregister_ram() routines. This flag is then used by the
> migration to identify RAMBlocks to discard on the source. Some checks
> are also performed on the destination to make sure nothing invalid was
> sent.
>
> Signed-off-by: Cédric Le Goater <c...@kaod.org>
Hi Cédric,
Yes, this is looking nicer; the macro makes the changes quite small.
A couple of questions:
> ---
>
> Changes since v1:
>
> - introduced a new RAMBlock flag RAM_MIGRATABLE
> - fixed RAMBLOCK_FOREACH_MIGRATABLE() macro to handle code that
> omitted {}.
>
> exec.c | 10 ++++++++++
> include/exec/cpu-common.h | 1 +
> migration/ram.c | 42 ++++++++++++++++++++++++++++++++----------
> 3 files changed, 43 insertions(+), 10 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index 02b1efebb7c3..e9432c06294e 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -104,6 +104,9 @@ static MemoryRegion io_mem_unassigned;
> * (Set during postcopy)
> */
> #define RAM_UF_ZEROPAGE (1 << 3)
> +
> +/* RAM can be migrated */
> +#define RAM_MIGRATABLE (1 << 4)
> #endif
>
> #ifdef TARGET_PAGE_BITS_VARY
> @@ -1807,6 +1810,11 @@ void qemu_ram_set_uf_zeroable(RAMBlock *rb)
> rb->flags |= RAM_UF_ZEROPAGE;
> }
>
> +bool qemu_ram_is_migratable(RAMBlock *rb)
> +{
> + return rb->flags & RAM_MIGRATABLE;
> +}
> +
> /* Called with iothread lock held. */
> void qemu_ram_set_idstr(RAMBlock *new_block, const char *name, DeviceState
> *dev)
> {
> @@ -1823,6 +1831,7 @@ void qemu_ram_set_idstr(RAMBlock *new_block, const char
> *name, DeviceState *dev)
> }
> }
> pstrcat(new_block->idstr, sizeof(new_block->idstr), name);
> + new_block->flags |= RAM_MIGRATABLE;
>
> rcu_read_lock();
> RAMBLOCK_FOREACH(block) {
> @@ -1845,6 +1854,7 @@ void qemu_ram_unset_idstr(RAMBlock *block)
> */
> if (block) {
> memset(block->idstr, 0, sizeof(block->idstr));
> + block->flags &= ~RAM_MIGRATABLE;
> }
> }
Why in qemu_ram_set_idstr and qemu_ram_(un)set_idstr ? It seems an
odd place to put them.
> diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
> index 24d335f95d45..96854519b514 100644
> --- a/include/exec/cpu-common.h
> +++ b/include/exec/cpu-common.h
> @@ -75,6 +75,7 @@ const char *qemu_ram_get_idstr(RAMBlock *rb);
> bool qemu_ram_is_shared(RAMBlock *rb);
> bool qemu_ram_is_uf_zeroable(RAMBlock *rb);
> void qemu_ram_set_uf_zeroable(RAMBlock *rb);
> +bool qemu_ram_is_migratable(RAMBlock *rb);
>
> size_t qemu_ram_pagesize(RAMBlock *block);
> size_t qemu_ram_pagesize_largest(void);
> diff --git a/migration/ram.c b/migration/ram.c
> index 0e90efa09236..89c3accc4e26 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -187,6 +187,11 @@ void ramblock_recv_bitmap_set_range(RAMBlock *rb, void
> *host_addr,
> nr);
> }
>
> +/* Should be holding either ram_list.mutex, or the RCU lock. */
> +#define RAMBLOCK_FOREACH_MIGRATABLE(block) \
> + RAMBLOCK_FOREACH(block) \
> + if (!qemu_ram_is_migratable(block)) {} else
> +
> /*
> * An outstanding page request, on the source, having been received
> * and queued
> @@ -780,6 +785,10 @@ unsigned long migration_bitmap_find_dirty(RAMState *rs,
> RAMBlock *rb,
> unsigned long *bitmap = rb->bmap;
> unsigned long next;
>
> + if (!qemu_ram_is_migratable(rb)) {
> + return size;
> + }
> +
> if (rs->ram_bulk_stage && start > 0) {
> next = start + 1;
> } else {
> @@ -825,7 +834,7 @@ uint64_t ram_pagesize_summary(void)
> RAMBlock *block;
> uint64_t summary = 0;
>
> - RAMBLOCK_FOREACH(block) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> summary |= block->page_size;
> }
>
> @@ -849,7 +858,7 @@ static void migration_bitmap_sync(RAMState *rs)
>
> qemu_mutex_lock(&rs->bitmap_mutex);
> rcu_read_lock();
> - RAMBLOCK_FOREACH(block) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> migration_bitmap_sync_range(rs, block, 0, block->used_length);
> }
> rcu_read_unlock();
> @@ -1499,6 +1508,10 @@ static int ram_save_host_page(RAMState *rs,
> PageSearchStatus *pss,
> size_t pagesize_bits =
> qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
>
> + if (!qemu_ram_is_migratable(pss->block)) {
> + return 0;
> + }
> +
We might want to print a diagnostic there - it shouldn't happen right?
> do {
> tmppages = ram_save_target_page(rs, pss, last_stage);
> if (tmppages < 0) {
> @@ -1587,7 +1600,7 @@ uint64_t ram_bytes_total(void)
> uint64_t total = 0;
>
> rcu_read_lock();
> - RAMBLOCK_FOREACH(block) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> total += block->used_length;
> }
> rcu_read_unlock();
> @@ -1642,7 +1655,7 @@ static void ram_save_cleanup(void *opaque)
> */
> memory_global_dirty_log_stop();
>
> - QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> g_free(block->bmap);
> block->bmap = NULL;
> g_free(block->unsentmap);
> @@ -1705,7 +1718,7 @@ void
> ram_postcopy_migrated_memory_release(MigrationState *ms)
> {
> struct RAMBlock *block;
>
> - RAMBLOCK_FOREACH(block) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> unsigned long *bitmap = block->bmap;
> unsigned long range = block->used_length >> TARGET_PAGE_BITS;
> unsigned long run_start = find_next_zero_bit(bitmap, range, 0);
> @@ -1783,7 +1796,7 @@ static int
> postcopy_each_ram_send_discard(MigrationState *ms)
> struct RAMBlock *block;
> int ret;
>
> - RAMBLOCK_FOREACH(block) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> PostcopyDiscardState *pds =
> postcopy_discard_send_init(ms, block->idstr);
>
> @@ -1991,7 +2004,7 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms)
> rs->last_sent_block = NULL;
> rs->last_page = 0;
>
> - QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> unsigned long pages = block->used_length >> TARGET_PAGE_BITS;
> unsigned long *bitmap = block->bmap;
> unsigned long *unsentmap = block->unsentmap;
> @@ -2150,7 +2163,7 @@ static void ram_list_init_bitmaps(void)
>
> /* Skip setting bitmap if there is no RAM */
> if (ram_bytes_total()) {
> - QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> pages = block->max_length >> TARGET_PAGE_BITS;
> block->bmap = bitmap_new(pages);
> bitmap_set(block->bmap, 0, pages);
> @@ -2226,7 +2239,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>
> qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE);
>
> - RAMBLOCK_FOREACH(block) {
> + RAMBLOCK_FOREACH_MIGRATABLE(block) {
> qemu_put_byte(f, strlen(block->idstr));
> qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
> qemu_put_be64(f, block->used_length);
Good, that's all quite neat; we've just got to watch out we don't
accidentally add any RAMBLOCK_FOREACH's back.
> @@ -2471,6 +2484,11 @@ static inline RAMBlock *ram_block_from_stream(QEMUFile
> *f, int flags)
> return NULL;
> }
>
> + if (!qemu_ram_is_migratable(block)) {
> + error_report("block %s should not be migrated !", id);
> + return NULL;
> + }
> +
> return block;
> }
>
> @@ -2921,7 +2939,11 @@ static int ram_load(QEMUFile *f, void *opaque, int
> version_id)
> length = qemu_get_be64(f);
>
> block = qemu_ram_block_by_name(id);
> - if (block) {
> + if (block && !qemu_ram_is_migratable(block)) {
> + error_report("block %s should not be migrated !", id);
> + ret = -EINVAL;
> +
> + } else if (block) {
> if (length != block->used_length) {
> Error *local_err = NULL;
>
> --
> 2.13.6
Dave
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
