Il 17/07/2013 11:50, Markus Armbruster ha scritto:
> Richard Henderson <[email protected]> writes:
>
>> Honor the implementation maximum access size, and at least check
>> the minimum access size.
>>
>> Reviewed-by: Paolo Bonzini <[email protected]>
>> Signed-off-by: Richard Henderson <[email protected]>
>
> Fails for me:
>
> qemu-system-x86_64: /work/armbru/qemu/exec.c:1927: memory_access_size:
> Assertion `l >= access_size_min' failed.
This:
unsigned access_size_min = mr->ops->impl.min_access_size;
unsigned access_size_max = mr->ops->impl.max_access_size;
must be respectively:
unsigned access_size_min = 1;
unsigned access_size_max = mr->ops->valid.max_access_size;
access_size_min can be 1 because erroneous accesses must not crash
QEMU, they should trigger exceptions in the guest or just return
garbage (depending on the CPU). I'm not sure I understand the comment,
placing a 4-byte field at the last byte of a region makes no sense
(unless impl.unaligned is true).
access_size_max can be mr->ops->valid.max_access_size because memory.c
can and will still break accesses bigger than
mr->ops->impl.max_access_size.
Markus, can you try the minimal patch above? Or this one that also
does the consequent simplifications.
diff --git a/exec.c b/exec.c
index c99a883..0904283 100644
--- a/exec.c
+++ b/exec.c
@@ -1898,14 +1898,8 @@ static inline bool memory_access_is_direct(MemoryRegion
*mr, bool is_write)
static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
{
- unsigned access_size_min = mr->ops->impl.min_access_size;
- unsigned access_size_max = mr->ops->impl.max_access_size;
+ unsigned access_size_max = mr->ops->valid.max_access_size;
- /* Regions are assumed to support 1-4 byte accesses unless
- otherwise specified. */
- if (access_size_min == 0) {
- access_size_min = 1;
- }
if (access_size_max == 0) {
access_size_max = 4;
}
@@ -1922,9 +1916,6 @@ static int memory_access_size(MemoryRegion *mr, unsigned
l, hwaddr addr)
if (l > access_size_max) {
l = access_size_max;
}
- /* ??? The users of this function are wrong, not supporting minimums larger
- than the remaining length. C.f. memory.c:access_with_adjusted_size. */
- assert(l >= access_size_min);
return l;
}
Paolo
