mem-ruby,sim: Add support for VGA ROM memory region

Checks if the address is in a shadowed region, and sends the request
to pio to be serviced by the device backing up that range.

Based on: https://gem5-review.googlesource.com/c/amd/gem5/+/23484

Change-Id: I4d5b46cccd6203523008b2e9545d55eb62130964
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/46159
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

configs/example/gpufs/system/system.py

@@ -75,6 +75,9 @@ def makeGpuFSSystem(args):
                                              voltage_domain =
                                              system.cpu_voltage_domain)
 
+    # Setup VGA ROM region
+    system.shadow_rom_ranges = [AddrRange(0xc0000, size = Addr('128kB'))]
+
     # Create specified number of CPUs. GPUFS really only needs one.
     system.cpu = [TestCPUClass(clk_domain=system.cpu_clk_domain, cpu_id=i)
                     for i in range(args.num_cpus)]

src/mem/ruby/system/RubyPort.cc

@@ -606,12 +606,28 @@ RubyPort::PioResponsePort::getAddrRanges() const
     return ranges;
 }
 
+bool
+RubyPort::MemResponsePort::isShadowRomAddress(Addr addr) const
+{
+    RubyPort *ruby_port = static_cast<RubyPort *>(&owner);
+    AddrRangeList ranges = ruby_port->system->getShadowRomRanges();
+
+    for (auto it = ranges.begin(); it != ranges.end(); ++it) {
+        if (it->contains(addr)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 bool
 RubyPort::MemResponsePort::isPhysMemAddress(PacketPtr pkt) const
 {
     RubyPort *ruby_port = static_cast<RubyPort *>(&owner);
-    return ruby_port->system->isMemAddr(pkt->getAddr())
-        || ruby_port->system->isDeviceMemAddr(pkt);
+    Addr addr = pkt->getAddr();
+    return (ruby_port->system->isMemAddr(addr) && !isShadowRomAddress(addr))
+           || ruby_port->system->isDeviceMemAddr(pkt);
 }
 
 void

src/mem/ruby/system/RubyPort.hh

@@ -99,6 +99,7 @@ class RubyPort : public ClockedObject
         void addToRetryList();
 
       private:
+        bool isShadowRomAddress(Addr addr) const;
         bool isPhysMemAddress(PacketPtr pkt) const;
     };
 

src/sim/System.py

@@ -83,6 +83,10 @@ class System(SimObject):
     # I/O bridge or cache
     mem_ranges = VectorParam.AddrRange([], "Ranges that constitute main memory")
 
+    # The ranges backed by a shadowed ROM
+    shadow_rom_ranges = VectorParam.AddrRange([], "Ranges  backed by a " \
+                                                  "shadowed ROM")
+
     shared_backstore = Param.String("", "backstore's shmem segment filename, "
         "use to directly address the backstore from another host-OS process. "
         "Leave this empty to unset the MAP_SHARED flag.")

src/sim/system.cc

@@ -202,6 +202,8 @@ System::System(const Params &p)
 #endif
       physmem(name() + ".physmem", p.memories, p.mmap_using_noreserve,
               p.shared_backstore),
+      ShadowRomRanges(p.shadow_rom_ranges.begin(),
+                      p.shadow_rom_ranges.end()),
       memoryMode(p.mem_mode),
       _cacheLineSize(p.cache_line_size),
       numWorkIds(p.num_work_ids),

src/sim/system.hh

@@ -378,6 +378,13 @@ class System : public SimObject, public PCEventScope
      */
     AbstractMemory *getDeviceMemory(RequestorID _id) const;
 
+    /*
+     * Return the list of address ranges backed by a shadowed ROM.
+     *
+     * @return List of address ranges backed by a shadowed ROM
+     */
+    AddrRangeList getShadowRomRanges() const { return ShadowRomRanges; }
+
     /**
      * Get the architecture.
      */
@@ -413,6 +420,8 @@ class System : public SimObject, public PCEventScope
 
     PhysicalMemory physmem;
 
+    AddrRangeList ShadowRomRanges;
+
     enums::MemoryMode memoryMode;
 
     const unsigned int _cacheLineSize;