[v7,04/13] confidential guest support: Move side effect out of machine_set_memory_encryption()

Commit Message

David Gibson Jan. 13, 2021, 11:58 p.m. UTC

When the "memory-encryption" property is set, we also disable KSM
merging for the guest, since it won't accomplish anything.

We want that, but doing it in the property set function itself is
thereoretically incorrect, in the unlikely event of some configuration
environment that set the property then cleared it again before
constructing the guest.

More importantly, it makes some other cleanups we want more difficult.
So, instead move this logic to machine_run_board_init() conditional on
the final value of the property.

Signed-off-by: David Gibson <[e-mail]>
Reviewed-by: Richard Henderson <[e-mail]>
Reviewed-by: Greg Kurz <[e-mail]>
---
 hw/core/machine.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

Comments

Cornelia Huck Jan. 15, 2021, 12:56 p.m. UTC | #1

On Thu, 14 Jan 2021 10:58:02 +1100
David Gibson <[e-mail]> wrote:

> When the "memory-encryption" property is set, we also disable KSM
> merging for the guest, since it won't accomplish anything.
> 
> We want that, but doing it in the property set function itself is
> thereoretically incorrect, in the unlikely event of some configuration
> environment that set the property then cleared it again before
> constructing the guest.
> 
> More importantly, it makes some other cleanups we want more difficult.
> So, instead move this logic to machine_run_board_init() conditional on
> the final value of the property.
> 
> Signed-off-by: David Gibson <[e-mail]>
> Reviewed-by: Richard Henderson <[e-mail]>
> Reviewed-by: Greg Kurz <[e-mail]>
> ---
>  hw/core/machine.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)

Reviewed-by: Cornelia Huck <[e-mail]>

Patch

diff --git a/hw/core/machine.c b/hw/core/machine.c
index de3b8f1b31..8909117d80 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -437,14 +437,6 @@  static void machine_set_memory_encryption(Object *obj, const char *value,
 
     g_free(ms->memory_encryption);
     ms->memory_encryption = g_strdup(value);
-
-    /*
-     * With memory encryption, the host can't see the real contents of RAM,
-     * so there's no point in it trying to merge areas.
-     */
-    if (value) {
-        machine_set_mem_merge(obj, false, errp);
-    }
 }
 
 static bool machine_get_nvdimm(Object *obj, Error **errp)
@@ -1166,6 +1158,15 @@  void machine_run_board_init(MachineState *machine)
                     cc->deprecation_note);
     }
 
+    if (machine->memory_encryption) {
+        /*
+         * With memory encryption, the host can't see the real
+         * contents of RAM, so there's no point in it trying to merge
+         * areas.
+         */
+        machine_set_mem_merge(OBJECT(machine), false, &error_abort);
+    }
+
     machine_class->init(machine);
     phase_advance(PHASE_MACHINE_INITIALIZED);
 }