We want to actually use resizeable allocations in resizeable ram blocks
(IOW, make everything between used_length and max_length inaccessible) -
however, not all ram block notifiers can support that.

Introduce a way to detect if any registered notifier does not
support resizes - ram_block_notifiers_support_resize() - which we can later
use to fallback to legacy handling if a registered notifier (esp., SEV and
HAX) does not support actual resizes.

Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/core/numa.c         | 12 ++++++++++++
 include/exec/ramlist.h |  1 +
 2 files changed, 13 insertions(+)

diff --git a/hw/core/numa.c b/hw/core/numa.c
index 37ce175e13..1d5288c22c 100644
--- a/hw/core/numa.c
+++ b/hw/core/numa.c
@@ -914,3 +914,15 @@ void ram_block_notify_resize(void *host, size_t old_size, size_t new_size)
         }
     }
 }
+
+bool ram_block_notifiers_support_resize(void)
+{
+    RAMBlockNotifier *notifier;
+
+    QLIST_FOREACH(notifier, &ram_list.ramblock_notifiers, next) {
+        if (!notifier->ram_block_resized) {
+            return false;
+        }
+    }
+    return true;
+}
diff --git a/include/exec/ramlist.h b/include/exec/ramlist.h
index 293c0ddabe..ac5811be96 100644
--- a/include/exec/ramlist.h
+++ b/include/exec/ramlist.h
@@ -79,6 +79,7 @@ void ram_block_notifier_remove(RAMBlockNotifier *n);
 void ram_block_notify_add(void *host, size_t size, size_t max_size);
 void ram_block_notify_remove(void *host, size_t size, size_t max_size);
 void ram_block_notify_resize(void *host, size_t old_size, size_t new_size);
+bool ram_block_notifiers_support_resize(void);
 
 void ram_block_dump(Monitor *mon);
 
-- 
2.24.1

On Thursday, March 5, 2020 11:29:44 AM -03 David Hildenbrand wrote:
> We want to actually use resizeable allocations in resizeable ram blocks
> (IOW, make everything between used_length and max_length inaccessible) -
> however, not all ram block notifiers can support that.
>
> Introduce a way to detect if any registered notifier does not
> support resizes - ram_block_notifiers_support_resize() - which we can later
> use to fallback to legacy handling if a registered notifier (esp., SEV and
> HAX) does not support actual resizes.
>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---

Acked-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>

>  hw/core/numa.c         | 12 ++++++++++++
>  include/exec/ramlist.h |  1 +
>  2 files changed, 13 insertions(+)
>
> diff --git a/hw/core/numa.c b/hw/core/numa.c
> index 37ce175e13..1d5288c22c 100644
> --- a/hw/core/numa.c
> +++ b/hw/core/numa.c
> @@ -914,3 +914,15 @@ void ram_block_notify_resize(void *host, size_t
> old_size, size_t new_size) }
>      }
>  }
> +
> +bool ram_block_notifiers_support_resize(void)
> +{
> +    RAMBlockNotifier *notifier;
> +
> +    QLIST_FOREACH(notifier, &ram_list.ramblock_notifiers, next) {
> +        if (!notifier->ram_block_resized) {
> +            return false;
> +        }
> +    }
> +    return true;
> +}
> diff --git a/include/exec/ramlist.h b/include/exec/ramlist.h
> index 293c0ddabe..ac5811be96 100644
> --- a/include/exec/ramlist.h
> +++ b/include/exec/ramlist.h
> @@ -79,6 +79,7 @@ void ram_block_notifier_remove(RAMBlockNotifier *n);
>  void ram_block_notify_add(void *host, size_t size, size_t max_size);
>  void ram_block_notify_remove(void *host, size_t size, size_t max_size);
>  void ram_block_notify_resize(void *host, size_t old_size, size_t new_size);
> +bool ram_block_notifiers_support_resize(void);
>
>  void ram_block_dump(Monitor *mon);


--
Murilo