[Qemu-devel] Re: [RFC PATCH 5/6] savevm: Migrate RAM based on name/offset

[Anthony Liguori <anthony@codemonkey.ws>]

On 06/08/2010 02:16 PM, Alex Williamson wrote:
> Synchronize RAM blocks with the target and migrate using name/offset
> pairs.  This ensures both source and target have the same view of
> RAM and that we get the right bits into the right slot.
>
> Signed-off-by: Alex Williamson<alex.williamson@redhat.com>
> ---
>
>   arch_init.c |  103 +++++++++++++++++++++++++++++++++++++++++++++++++++++------
>   vl.c        |    2 +
>   2 files changed, 93 insertions(+), 12 deletions(-)
>
> diff --git a/arch_init.c b/arch_init.c
> index 6103461..8ba92ec 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -113,20 +113,29 @@ static int ram_save_block(QEMUFile *f)
>
>       while (addr<  total_ram) {
>           if (cpu_physical_memory_get_dirty(current_addr, MIGRATION_DIRTY_FLAG)) {
> +            RAMBlock *block;
> +            ram_addr_t offset;
>               uint8_t *p;
>
>               cpu_physical_memory_reset_dirty(current_addr,
>                                               current_addr + TARGET_PAGE_SIZE,
>                                               MIGRATION_DIRTY_FLAG);
>
> -            p = qemu_get_ram_ptr(current_addr);
> +            QLIST_FOREACH(block,&ram.blocks, next) {
> +                if (current_addr - block->offset<  block->length)
> +                    break;
> +            }
> +            offset = current_addr - block->offset;
> +            p = block->host + offset;
>
>               if (is_dup_page(p, *p)) {
> -                qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_COMPRESS);
> +                qemu_put_be64(f, offset | RAM_SAVE_FLAG_COMPRESS);
> +                qemu_put_buffer(f, (uint8_t *)block->name, sizeof(block->name));
>                   qemu_put_byte(f, *p);
>    

I think we could use some trickery like use another flag in 
current_address to determine whether this was a different section from 
the previous section and then only encode the section name if that's true.

Regards,

Anthony Liguori

>                   bytes_sent = 1;
>               } else {
> -                qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_PAGE);
> +                qemu_put_be64(f, offset | RAM_SAVE_FLAG_PAGE);
> +                qemu_put_buffer(f, (uint8_t *)block->name, sizeof(block->name));
>                   qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
>                   bytes_sent = TARGET_PAGE_SIZE;
>               }
> @@ -196,6 +205,7 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
>       }
>
>       if (stage == 1) {
> +        RAMBlock *block;
>           uint64_t total_ram = ram_bytes_total();
>           bytes_transferred = 0;
>
> @@ -210,6 +220,11 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
>           cpu_physical_memory_set_dirty_tracking(1);
>
>           qemu_put_be64(f, total_ram | RAM_SAVE_FLAG_MEM_SIZE);
> +
> +        QLIST_FOREACH(block,&ram.blocks, next) {
> +            qemu_put_buffer(f, (uint8_t *)block->name, sizeof(block->name));
> +            qemu_put_be64(f, block->length);
> +        }
>       }
>
>       bytes_transferred_last = bytes_transferred;
> @@ -257,7 +272,7 @@ int ram_load(QEMUFile *f, void *opaque, int version_id)
>       ram_addr_t addr;
>       int flags;
>
> -    if (version_id != 3) {
> +    if (version_id<  3) {
>           return -EINVAL;
>       }
>
> @@ -268,23 +283,89 @@ int ram_load(QEMUFile *f, void *opaque, int version_id)
>           addr&= TARGET_PAGE_MASK;
>
>           if (flags&  RAM_SAVE_FLAG_MEM_SIZE) {
> -            if (addr != ram_bytes_total()) {
> -                return -EINVAL;
> +            if (version_id == 3) {
> +                if (addr != ram_bytes_total()) {
> +                    return -EINVAL;
> +                }
> +            } else {
> +                /* Synchronize RAM block list */
> +                char name[64];
> +                ram_addr_t length;
> +                ram_addr_t total_ram_bytes = addr;
> +
> +                while (total_ram_bytes) {
> +                    RAMBlock *block;
> +                    qemu_get_buffer(f, (uint8_t *)name, sizeof(name));
> +                    length = qemu_get_be64(f);
> +
> +                    QLIST_FOREACH(block,&ram.blocks, next) {
> +                        if (!strncmp(name, block->name, sizeof(name))) {
> +                            if (block->length != length)
> +                                return -EINVAL;
> +                            break;
> +                        }
> +                    }
> +
> +                    if (!block) {
> +                        if (!qemu_ram_alloc(name, length))
> +                            return -ENOMEM;
> +                    }
> +
> +                    total_ram_bytes -= length;
> +                }
>               }
>           }
>
>           if (flags&  RAM_SAVE_FLAG_COMPRESS) {
> -            uint8_t ch = qemu_get_byte(f);
> -            memset(qemu_get_ram_ptr(addr), ch, TARGET_PAGE_SIZE);
> +            void *host;
> +            uint8_t ch;
> +
> +            if (version_id == 3) {
> +                host = qemu_get_ram_ptr(addr);
> +            } else {
> +                RAMBlock *block;
> +                char name[64];
> +
> +                qemu_get_buffer(f, (uint8_t *)name, sizeof(name));
> +
> +                QLIST_FOREACH(block,&ram.blocks, next) {
> +                    if (!strncmp(name, block->name, sizeof(name)))
> +                        break;
> +                }
> +                if (!block)
> +                    return -EINVAL;
> +
> +                host = block->host + addr;
> +            }
> +            ch = qemu_get_byte(f);
> +            memset(host, ch, TARGET_PAGE_SIZE);
>   #ifndef _WIN32
>               if (ch == 0&&
>                   (!kvm_enabled() || kvm_has_sync_mmu())) {
> -                madvise(qemu_get_ram_ptr(addr), TARGET_PAGE_SIZE,
> -                        MADV_DONTNEED);
> +                madvise(host, TARGET_PAGE_SIZE, MADV_DONTNEED);
>               }
>   #endif
>           } else if (flags&  RAM_SAVE_FLAG_PAGE) {
> -            qemu_get_buffer(f, qemu_get_ram_ptr(addr), TARGET_PAGE_SIZE);
> +            void *host;
> +
> +            if (version_id == 3) {
> +                host = qemu_get_ram_ptr(addr);
> +            } else {
> +                RAMBlock *block;
> +                char name[64];
> +
> +                qemu_get_buffer(f, (uint8_t *)name, sizeof(name));
> +
> +                QLIST_FOREACH(block,&ram.blocks, next) {
> +                    if (!strncmp(name, block->name, sizeof(name)))
> +                        break;
> +                }
> +                if (!block)
> +                    return -EINVAL;
> +
> +                host = block->host + addr;
> +            }
> +            qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
>           }
>           if (qemu_file_has_error(f)) {
>               return -EIO;
> diff --git a/vl.c b/vl.c
> index 9e9c176..a871895 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3731,7 +3731,7 @@ int main(int argc, char **argv, char **envp)
>       if (qemu_opts_foreach(&qemu_drive_opts, drive_init_func, machine, 1) != 0)
>           exit(1);
>
> -    register_savevm_live("ram", 0, 3, NULL, ram_save_live, NULL,
> +    register_savevm_live("ram", 0, 4, NULL, ram_save_live, NULL,
>                            ram_load, NULL);
>
>       if (nb_numa_nodes>  0) {
>
>