Rather than retaining io_mem_read/write as simple wrappers around
the memory_region_dispatch_read/write functions, make the latter
public and change all the callers to use them, since we need to
touch all the callsites anyway to add MemTxAttrs and MemTxResult
support. Delete io_mem_read and io_mem_write entirely.
(All the callers currently pass MEMTXATTRS_UNSPECIFIED
and convert the return value back to bool or ignore it.)
Backports commit 3b6434953934e6d4a776ed426d8c6d6badee176f from qemu
Define an API so that devices can register MemoryRegionOps whose read
and write callback functions are passed an arbitrary pointer to some
transaction attributes and can return a success-or-failure status code.
This will allow us to model devices which:
* behave differently for ARM Secure/NonSecure memory accesses
* behave differently for privileged/unprivileged accesses
* may return a transaction failure (causing a guest exception)
for erroneous accesses
This patch defines the new API and plumbs the attributes parameter through
to the memory.c public level functions io_mem_read() and io_mem_write(),
where it is currently dummied out.
The success/failure response indication is also propagated out to
io_mem_read() and io_mem_write(), which retain the old-style
boolean true-for-error return.
Backports commit cc05c43ad942165ecc6ffd39e41991bee43af044 from qemu
