dev-amdgpu: Update SDMA checkpointing

Patch https://gem5-review.googlesource.com/c/public/gem5/+/70040 added
support for a variable number of SDMA engines to support newer GPU
models. As part of this an SDMA IDs map was added to map from SDMA ID
number to the SDMA SimObject pointer. In order to get the correct
pointer in unserialize now, we need to store the ID in the checkpoint
and use that to index the new map. We can't simply assign using the loop
variable as the SDMAs might not be in order in the checkpoint and
additionally the checkpoint contains both the gfx and page offset for
the SDMA engines, so each SDMA is inserted into the SDMA offset map
(sdmaEngs) twice.

Change-Id: I08e9a8d785f467b6eebff8ab0a9336851c87258d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/70878
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>

src/dev/amdgpu/amdgpu_device.cc

@@ -604,7 +604,7 @@ AMDGPUDevice::serialize(CheckpointOut &cp) const
     idx = 0;
     for (auto & it : sdmaEngs) {
         sdma_engs_offset[idx] = it.first;
-        sdma_engs[idx] = idx;
+        sdma_engs[idx] = it.second->getId();
         ++idx;
     }
 
@@ -675,8 +675,9 @@ AMDGPUDevice::unserialize(CheckpointIn &cp)
         UNSERIALIZE_ARRAY(sdma_engs, sizeof(sdma_engs)/sizeof(sdma_engs[0]));
 
         for (int idx = 0; idx < sdma_engs_size; ++idx) {
-            assert(sdmaIds.count(idx));
-            SDMAEngine *sdma = sdmaIds[idx];
+            int sdma_id = sdma_engs[idx];
+            assert(sdmaIds.count(sdma_id));
+            SDMAEngine *sdma = sdmaIds[sdma_id];
             sdmaEngs.insert(std::make_pair(sdma_engs_offset[idx], sdma));
         }
     }

src/dev/amdgpu/sdma_engine.hh

@@ -165,6 +165,7 @@ class SDMAEngine : public DmaVirtDevice
     void setGPUDevice(AMDGPUDevice *gpu_device);
 
     void setId(int _id) { id = _id; }
+    int getId() const { return id; }
     /**
      * Returns the client id for the Interrupt Handler.
      */