On 12/06/2018 21:05, Eric Auger wrote: > When an IOMMUMemoryRegion is in front of a virtio device, > address_space_cache_init does not set cache->ptr as the memory > region is not RAM. However when the device performs an access, > we end up in glue() which performs the translation and then uses > MAP_RAM. This latter uses the unset ptr and returns a wrong value > which leads to a SIGSEV in address_space_lduw_internal_cached_slow, > for instance. Let's test whether the cache->ptr is set, and in > the negative use the old macro definition. This fixes the > use cases featuring vIOMMU (Intel and ARM SMMU) which lead to > a SIGSEV. > > Fixes: 48564041a73a (exec: reintroduce MemoryRegion caching) > Signed-off-by: Eric Auger <eric.au...@redhat.com> > > --- > > I am not sure whether it doesn't break any targeted optimization > but at least it removes the SIGSEV.
Actually cache->ptr is always NULL here, since this is the slow path (there is even an assertion in address_space_translate_cached); so MAP_RAM can be even simpler and, apart from the bugfix, I think we should remove all of IS_DIRECT, MAP_RAM and INVALIDATE as a follow-up. They were needed in the original implementation of MemoryRegionCache, which only worked with RAM regions but not anymore now that the RAM case is open-coded in include/exec/memory_ldst_cached.inc.h. Thanks, Paolo > Signed-off-by: Eric Auger <eric.au...@redhat.com> > --- > exec.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/exec.c b/exec.c > index f6645ed..46fbd25 100644 > --- a/exec.c > +++ b/exec.c > @@ -3800,7 +3800,9 @@ address_space_write_cached_slow(MemoryRegionCache > *cache, hwaddr addr, > #define SUFFIX _cached_slow > #define TRANSLATE(...) address_space_translate_cached(cache, > __VA_ARGS__) > #define IS_DIRECT(mr, is_write) memory_access_is_direct(mr, is_write) > -#define MAP_RAM(mr, ofs) (cache->ptr + (ofs - cache->xlat)) > +#define MAP_RAM(mr, ofs) (cache->ptr ? \ > + (cache->ptr + (ofs - cache->xlat)) : \ > + qemu_map_ram_ptr((mr)->ram_block, ofs)) > #define INVALIDATE(mr, ofs, len) invalidate_and_set_dirty(mr, ofs, len) > #define RCU_READ_LOCK() ((void)0) > #define RCU_READ_UNLOCK() ((void)0) >