Since commit 2cdfcf272d ("memory: assign MemoryRegionOps to all regions"), all newly created regions are assigned with unassigned_mem_ops (which might be then overwritten).
When using aliased container regions, and there is no region mapped at address 0 in the container, the memory_region_dispatch_read() and memory_region_dispatch_write() calls incorrectly return the container unassigned_mem_ops, because the alias offset is not used. The memory_region_init_alias() flow is: memory_region_init_alias() -> memory_region_init() -> object_initialize(TYPE_MEMORY_REGION) -> memory_region_initfn() -> mr->ops = &unassigned_mem_ops; Later when accessing the alias, the memory_region_dispatch_read() flow is: memory_region_dispatch_read(offset) -> memory_region_access_valid(mr) <- offset is ignored -> mr->ops->valid.accepts() -> unassigned_mem_accepts() <- false <- false <- MEMTX_DECODE_ERROR The caller gets a MEMTX_DECODE_ERROR while the access is OK. Fix by dispatching aliases recusirvely, accessing its origin region after adding the alias offset. Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org> --- v3: - reworded, mentioning the "alias to container" case - use recursive call instead of while(), because easier when debugging therefore reset Richard R-b tag. v2: - use while() --- softmmu/memory.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/softmmu/memory.c b/softmmu/memory.c index d4493ef9e43..23bdbfac079 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -1442,6 +1442,11 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr, unsigned size = memop_size(op); MemTxResult r; + if (mr->alias) { + return memory_region_dispatch_read(mr->alias, + addr + mr->alias_offset, + pval, op, attrs); + } if (!memory_region_access_valid(mr, addr, size, false, attrs)) { *pval = unassigned_mem_read(mr, addr, size); return MEMTX_DECODE_ERROR; @@ -1486,6 +1491,11 @@ MemTxResult memory_region_dispatch_write(MemoryRegion *mr, { unsigned size = memop_size(op); + if (mr->alias) { + return memory_region_dispatch_write(mr->alias, + addr + mr->alias_offset, + data, op, attrs); + } if (!memory_region_access_valid(mr, addr, size, true, attrs)) { unassigned_mem_write(mr, addr, data, size); return MEMTX_DECODE_ERROR; -- 2.26.3