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Re: [Qemu-devel] [PATCH] migration: allow private destination ram with x
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH] migration: allow private destination ram with x-ignore-shared |
Date: |
Mon, 17 Jun 2019 11:46:02 +0100 |
User-agent: |
Mutt/1.11.4 (2019-03-13) |
* Peng Tao (address@hidden) wrote:
> By removing the share ram check, qemu is able to migrate
> to private destination ram when x-ignore-shared capability
> is on. Then we can create multiple destination VMs based
> on the same source VM.
>
> This changes the x-ignore-shared migration capability to
> work similar to Lai's original bypass-shared-memory
> work(https://lists.gnu.org/archive/html/qemu-devel/2018-04/msg00003.html)
> which enables kata containers (https://katacontainers.io)
> to implement the VM templating feature.
>
> An example usage in kata containers(https://katacontainers.io):
> 1. Start the source VM:
> qemu-system-x86 -m 2G \
> -object
> memory-backend-file,id=mem0,size=2G,share=on,mem-path=/tmpfs/template-memory \
> -numa node,memdev=mem0
> 2. Stop the template VM, set migration x-ignore-shared capability,
> migrate "exec:cat>/tmpfs/state", quit it
> 3. Start target VM:
> qemu-system-x86 -m 2G \
> -object
> memory-backend-file,id=mem0,size=2G,share=off,mem-path=/tmpfs/template-memory
> \
> -numa node,memdev=mem0 \
> -incoming defer
> 4. connect to target VM qmp, set migration x-ignore-shared capability,
> migrate_incoming "exec:cat /tmpfs/state"
> 5. create more target VMs repeating 3 and 4
>
> Cc: Dr. David Alan Gilbert <address@hidden>
> Cc: Yury Kotov <address@hidden>
> Cc: Jiangshan Lai <address@hidden>
> Cc: Xu Wang <address@hidden>
> Signed-off-by: Peng Tao <address@hidden>
I think this is OK, but please post this to qemu-devel.
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
> migration/ram.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 1ca9ba7..cdb82a3 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -3373,7 +3373,6 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
> }
> if (migrate_ignore_shared()) {
> qemu_put_be64(f, block->mr->addr);
> - qemu_put_byte(f, ramblock_is_ignored(block) ? 1 : 0);
> }
> }
>
> @@ -4340,12 +4339,6 @@ static int ram_load(QEMUFile *f, void *opaque, int
> version_id)
> }
> if (migrate_ignore_shared()) {
> hwaddr addr = qemu_get_be64(f);
> - bool ignored = qemu_get_byte(f);
> - if (ignored != ramblock_is_ignored(block)) {
> - error_report("RAM block %s should %s be
> migrated",
> - id, ignored ? "" : "not");
> - ret = -EINVAL;
> - }
> if (ramblock_is_ignored(block) &&
> block->mr->addr != addr) {
> error_report("Mismatched GPAs for block %s "
> --
> 1.8.3.1
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK