[PATCH v2 2/3] memory: fix PIO/MMIO-initiated dma-reentracy issues

[Alexander Bulekov]

Set/check the engaged_in_io DeviceState flag, prior to calling
MemoryRegion handlers.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
 softmmu/memory.c     | 15 +++++++++++++++
 softmmu/trace-events |  1 +
 2 files changed, 16 insertions(+)

diff --git a/softmmu/memory.c b/softmmu/memory.c
index 7ba2048836..44a14bb4f5 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -532,6 +532,7 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
     uint64_t access_mask;
     unsigned access_size;
     unsigned i;
+    DeviceState *dev = NULL;
     MemTxResult r = MEMTX_OK;
 
     if (!access_size_min) {
@@ -541,6 +542,17 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
         access_size_max = 4;
     }
 
+    /* Do not allow more than one simultanous access to a device's IO Regions 
*/
+    if (mr->owner &&
+        !mr->ram_device && !mr->ram && !mr->rom_device && !mr->readonly) {
+        dev = (DeviceState *) object_dynamic_cast(mr->owner, TYPE_DEVICE);
+        if (dev->engaged_in_io) {
+            trace_memory_region_reentrant_io(get_cpu_index(), mr, addr, size);
+            return MEMTX_ERROR;
+        }
+        dev->engaged_in_io = true;
+    }
+
     /* FIXME: support unaligned access? */
     access_size = MAX(MIN(size, access_size_max), access_size_min);
     access_mask = MAKE_64BIT_MASK(0, access_size * 8);
@@ -555,6 +567,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
                         access_mask, attrs);
         }
     }
+    if (dev) {
+        dev->engaged_in_io = false;
+    }
     return r;
 }
 
diff --git a/softmmu/trace-events b/softmmu/trace-events
index 9c88887b3c..d7228316db 100644
--- a/softmmu/trace-events
+++ b/softmmu/trace-events
@@ -13,6 +13,7 @@ memory_region_ops_read(int cpu_index, void *mr, uint64_t 
addr, uint64_t value, u
 memory_region_ops_write(int cpu_index, void *mr, uint64_t addr, uint64_t 
value, unsigned size, const char *name) "cpu %d mr %p addr 0x%"PRIx64" value 
0x%"PRIx64" size %u name '%s'"
 memory_region_subpage_read(int cpu_index, void *mr, uint64_t offset, uint64_t 
value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size 
%u"
 memory_region_subpage_write(int cpu_index, void *mr, uint64_t offset, uint64_t 
value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size 
%u"
+memory_region_reentrant_io(int cpu_index, void *mr, uint64_t offset, unsigned 
size) "cpu %d mr %p offset 0x%"PRIx64" size %u"
 memory_region_ram_device_read(int cpu_index, void *mr, uint64_t addr, uint64_t 
value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u"
 memory_region_ram_device_write(int cpu_index, void *mr, uint64_t addr, 
uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" 
size %u"
 memory_region_sync_dirty(const char *mr, const char *listener, int global) "mr 
'%s' listener '%s' synced (global=%d)"
-- 
2.33.0