Before sending this patch, I had
commit 71d15e90d513327c90d346ef73865d2db749fbba
Author: David Hildenbrand <da...@redhat.com>
Date: Thu Oct 7 11:25:18 2021 +0200
memory: make memory_region_is_mapped() succeed when mapped via an alias
memory_region_is_mapped() currently does not return "true" when a memory
region is mapped via an alias. Let's fix that by adding a
"mapped_via_alias" counter to memory regions and updating it accordingly
when an alias gets (un)mapped.
this needs a clarification,
is memory_region_is_mapped() used on aliased memory region or on alias?
I think right now it's barely used with aliases
(memory_region_is_mapped(alias)), at least I am not aware of users.
What's more likely is that the final memory region will be the target of
memory_region_is_mapped().
The question is: which semantics do we want to have so we can properly
document and eventually fix.
I am not aware of actual issues, this is rather a cleanup.
Signed-off-by: David Hildenbrand <da...@redhat.com>
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 75b4f600e3..93d0190202 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -728,6 +728,7 @@ struct MemoryRegion {
const MemoryRegionOps *ops;
void *opaque;
MemoryRegion *container;
+ int mapped_via_alias; /* Mapped via an alias, container might be NULL */
Int128 size;
hwaddr addr;
void (*destructor)(MemoryRegion *mr);
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 3bcfc3899b..1168a00819 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2535,8 +2535,13 @@ static void
memory_region_add_subregion_common(MemoryRegion *mr,
hwaddr offset,
MemoryRegion *subregion)
{
+ MemoryRegion *alias;
+
assert(!subregion->container);
subregion->container = mr;
+ for (alias = subregion->alias; alias; alias = alias->alias) {
+ alias->mapped_via_alias++;
it it necessary to update mapped_via_alias for intermediate aliases?
Why not just update on counter only on leaf (aliased region)?
Assume we have alias0 -> alias1 -> region and map alias0.
Once alias0 is mapped it will have ->container set and
memory_region_is_mapped(alias0) will return "true".
With my patch, both, "alias1" and the region will be marked
"mapped_via_alias" and memory_region_is_mapped() will succeed on both of
them. With what you propose, memory_region_is_mapped() would only
succeed on the region (well, and on alias 0) but not on alias1.
--
Thanks,
David / dhildenb
