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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 11:46:48 +0100 |
User-agent: |
Mutt/1.11.4 (2019-03-13) |
* Dr. David Alan Gilbert (address@hidden) wrote:
> * 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.
Oh you did :-) That's double fine then!
> 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
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK