Hi Paolo, On 06/13/2018 11:56 AM, Paolo Bonzini wrote: > 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.
OK I respinned with your suggestions. Hope it matches your expectations. Thanks Eric > > 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) >> > >
