[Qemu-devel] [PATCH] migration: allow private destination ram with x-ignore-shared

[Qemu-devel] [PATCH] migration: allow private destination ram with x-ignore-shared

[Peng Tao]

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 <dgilbert@redhat.com>
Cc: Yury Kotov <yury-kotov@yandex-team.ru>
Cc: Jiangshan Lai <laijs@hyper.sh>
Cc: Xu Wang <xu@hyper.sh>
Signed-off-by: Peng Tao <tao.peng@linux.alibaba.com>
---
 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

Re: [Qemu-devel] [PATCH] migration: allow private destination ram with x-ignore-shared

[Peng Tao]

On 2019/6/14 14:35, Peng Tao 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
> 
FYI, corresponding kata pull request is posted at 
https://github.com/kata-containers/runtime/pull/1799

Cheers,
Tao
-- 
Into something rich and strange.

Re: [Qemu-devel] [PATCH] migration: allow private destination ram with x-ignore-shared

[Dr. David Alan Gilbert]

* Peng Tao (tao.peng@linux.alibaba.com) 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 <dgilbert@redhat.com>
> Cc: Yury Kotov <yury-kotov@yandex-team.ru>
> Cc: Jiangshan Lai <laijs@hyper.sh>
> Cc: Xu Wang <xu@hyper.sh>
> Signed-off-by: Peng Tao <tao.peng@linux.alibaba.com>

I think this is OK, but please post this to qemu-devel.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  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 / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH] migration: allow private destination ram with x-ignore-shared

[Dr. David Alan Gilbert]

* Dr. David Alan Gilbert (dgilbert@redhat.com) wrote:
> * Peng Tao (tao.peng@linux.alibaba.com) 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 <dgilbert@redhat.com>
> > Cc: Yury Kotov <yury-kotov@yandex-team.ru>
> > Cc: Jiangshan Lai <laijs@hyper.sh>
> > Cc: Xu Wang <xu@hyper.sh>
> > Signed-off-by: Peng Tao <tao.peng@linux.alibaba.com>
> 
> 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 <dgilbert@redhat.com>
> 
> > ---
> >  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 / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK