diff mbox

[RFC,v2,4/6] hostmem: return recreated MemoryRegion if current can't be reused

Message ID 1433776757-61958-5-git-send-email-imammedo@redhat.com
State New
Headers show

Commit Message

Igor Mammedov June 8, 2015, 3:19 p.m. UTC 
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 backends/hostmem.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Paolo Bonzini June 8, 2015, 3:30 p.m. UTC | #1 
On 08/06/2015 17:19, Igor Mammedov wrote:
>  MemoryRegion *
>  host_memory_backend_get_memory(HostMemoryBackend *backend, Error **errp)
>  {
> +    UserCreatableClass *ucc = USER_CREATABLE_GET_CLASS(backend);
> +
> +    if (memory_region_is_hva_mapped(&backend->mr)) {
> +        object_unparent(OBJECT(&backend->mr));
> +        ucc->complete(USER_CREATABLE(backend), errp);
> +    }

I'm not sure I understand this, and the commit message... doesn't help.

Is it for the case where you unplug memory and then reuse the old
backend?  Can we just outlaw this, forcing each memory backend to be
used only once?

Paolo
Igor Mammedov June 8, 2015, 4:25 p.m. UTC | #2 
On Mon, 08 Jun 2015 17:30:20 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> 
> 
> On 08/06/2015 17:19, Igor Mammedov wrote:
> >  MemoryRegion *
> >  host_memory_backend_get_memory(HostMemoryBackend *backend, Error **errp)
> >  {
> > +    UserCreatableClass *ucc = USER_CREATABLE_GET_CLASS(backend);
> > +
> > +    if (memory_region_is_hva_mapped(&backend->mr)) {
> > +        object_unparent(OBJECT(&backend->mr));
> > +        ucc->complete(USER_CREATABLE(backend), errp);
> > +    }
> 
> I'm not sure I understand this, and the commit message... doesn't help.
> 
> Is it for the case where you unplug memory and then reuse the old
> backend?
yes

>  Can we just outlaw this, forcing each memory backend to be
> used only once?
to outlaw it gracefully without asserting QEMU during hotplug
user should be able to detect that it's outlawed i.e. use
memory_region_is_hva_mapped(), but yes we can.

> 
> Paolo
Paolo Bonzini June 8, 2015, 4:28 p.m. UTC | #3 
On 08/06/2015 18:25, Igor Mammedov wrote:
> 
>> >  Can we just outlaw this, forcing each memory backend to be
>> > used only once?
> to outlaw it gracefully without asserting QEMU during hotplug
> user should be able to detect that it's outlawed i.e. use
> memory_region_is_hva_mapped(), but yes we can.

We can also add a ->detach method to HostMemoryBackend, and forbid
get_memory after it has been invoked.

Paolo
diff mbox

Patch

diff --git a/backends/hostmem.c b/backends/hostmem.c
index 2a8614d..4486483 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -283,6 +283,12 @@  static void host_memory_backend_init(Object *obj)
 MemoryRegion *
 host_memory_backend_get_memory(HostMemoryBackend *backend, Error **errp)
 {
+    UserCreatableClass *ucc = USER_CREATABLE_GET_CLASS(backend);
+
+    if (memory_region_is_hva_mapped(&backend->mr)) {
+        object_unparent(OBJECT(&backend->mr));
+        ucc->complete(USER_CREATABLE(backend), errp);
+    }
     return memory_region_size(&backend->mr) ? &backend->mr : NULL;
 }