[gem5-dev] Change in gem5/gem5[develop]: dev: Make VirtIORng device use gem5's rng instead of C++'s

[Hoa Nguyen (Gerrit) via gem5-dev]

Hoa Nguyen has submitted this change. (  
https://gem5-review.googlesource.com/c/public/gem5/+/56889 )

Change subject: dev: Make VirtIORng device use gem5's rng instead of C++'s
......................................................................
dev: Make VirtIORng device use gem5's rng instead of C++'s

Currently, VirtIORng uses C++'s RNG. This causes nondeterminism
across simulations using this device. One example is the example RISC-V
board booting Ubuntu,

configs/example/gem5_library/riscv-ubuntu-run.py

JIRA: https://gem5.atlassian.net/browse/GEM5-1193

Change-Id: I299e72eb891819007b4260390f5c2ba94d2dec7b
Signed-off-by: Hoa Nguyen <hoangu...@ucdavis.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56889
Maintainer: Bobby Bruce <bbr...@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power...@gmail.com>
Tested-by: kokoro <noreply+kok...@google.com>
---
M src/dev/virtio/VirtIORng.py
M src/dev/virtio/rng.cc
M src/dev/virtio/rng.hh
3 files changed, 29 insertions(+), 36 deletions(-)

Approvals:
  Jason Lowe-Power: Looks good to me, approved
  Bobby Bruce: Looks good to me, approved
  kokoro: Regressions pass




diff --git a/src/dev/virtio/VirtIORng.py b/src/dev/virtio/VirtIORng.py
index 54848ee..13df059 100644
--- a/src/dev/virtio/VirtIORng.py
+++ b/src/dev/virtio/VirtIORng.py
@@ -46,5 +46,3 @@
     cxx_class = 'gem5::VirtIORng'

     qSize = Param.Unsigned(16, "Request queue size")
-
-    entropy_source = Param.String("/dev/random", "The source of entropy")
diff --git a/src/dev/virtio/rng.cc b/src/dev/virtio/rng.cc
index 50a747c..c26568e 100644
--- a/src/dev/virtio/rng.cc
+++ b/src/dev/virtio/rng.cc
@@ -38,9 +38,7 @@

 #include "dev/virtio/rng.hh"

-#include <fcntl.h>
-#include <unistd.h>
-
+#include "base/random.hh"
 #include "debug/VIORng.hh"
 #include "params/VirtIORng.hh"
 #include "sim/system.hh"
@@ -50,8 +48,7 @@

 VirtIORng::VirtIORng(const Params &params)
     : VirtIODeviceBase(params, ID_RNG, 0, 0),
-      qReq(params.system->physProxy, byteOrder, params.qSize,
-           params.entropy_source, *this)
+      qReq(params.system->physProxy, byteOrder, params.qSize, *this)
 {
     registerQueue(qReq);
 }
@@ -60,16 +57,10 @@
 {
 }

-VirtIORng::RngQueue::RngQueue(PortProxy &proxy, ByteOrder bo,
-    uint16_t size, const std::string &rng_file_path,
+VirtIORng::RngQueue::RngQueue(PortProxy &proxy, ByteOrder bo, uint16_t  
size,
     VirtIORng &_parent)
-    : VirtQueue(proxy, bo, size), parent(_parent), dist(0,255)
+    : VirtQueue(proxy, bo, size), parent(_parent)
 {
-    rng_fd = open(rng_file_path.c_str(), O_RDONLY);
-    if (rng_fd < 0) {
-        DPRINTF(VIORng, "error when open entropy source: %s\n",
-                rng_file_path.c_str());
-    }
 }

 void
@@ -89,16 +80,7 @@
         DPRINTF(VIORng, "Got descriptor (len: %i)\n", d->size());
         size_t len = 0;
         while (len < d->size()) {
-            uint8_t byte = 0;
-            bool rng_read_success = false;
-            if (rng_fd >= 0) {
-                ssize_t result = read(rng_fd, &byte, sizeof(uint8_t));
-                rng_read_success = (result > 0);
-            }
-            if (!rng_read_success) {
-                // fallback to C++ std rng generator
-                byte = dist(rd_device);
-            }
+            uint8_t byte = gem5::random_mt.random<uint8_t>();
             d->chainWrite(len, &byte, sizeof(uint8_t));
             ++len;
         }
diff --git a/src/dev/virtio/rng.hh b/src/dev/virtio/rng.hh
index 50a3723..7be2354 100644
--- a/src/dev/virtio/rng.hh
+++ b/src/dev/virtio/rng.hh
@@ -39,8 +39,6 @@
 #ifndef __DEV_VIRTIO_RNG_HH__
 #define __DEV_VIRTIO_RNG_HH__

-#include <random>
-
 #include "base/compiler.hh"
 #include "dev/virtio/base.hh"

@@ -76,9 +74,8 @@
         : public VirtQueue
     {
       public:
-        RngQueue(PortProxy &proxy, ByteOrder bo,
-                uint16_t size, const std::string &rng_file_path,
-                VirtIORng &_parent);
+        RngQueue(PortProxy &proxy, ByteOrder bo, uint16_t size,
+                 VirtIORng &_parent);
         virtual ~RngQueue() {}

         void onNotify() { trySend(); }
@@ -90,12 +87,6 @@

       protected:
         VirtIORng &parent;
-      private:
-        // system's special file for generating random number
-        int rng_fd;
-        // fallback random number generator
-        std::random_device rd_device;
-        std::uniform_int_distribution<int> dist;
     };
     /** Receive queue for port 0 */
     RngQueue qReq;

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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I299e72eb891819007b4260390f5c2ba94d2dec7b
Gerrit-Change-Number: 56889
Gerrit-PatchSet: 4
Gerrit-Owner: Hoa Nguyen <hoangu...@ucdavis.edu>
Gerrit-Reviewer: Bobby Bruce <bbr...@ucdavis.edu>
Gerrit-Reviewer: Gabe Black <gabe.bl...@gmail.com>
Gerrit-Reviewer: Hoa Nguyen <hoangu...@ucdavis.edu>
Gerrit-Reviewer: Jason Lowe-Power <power...@gmail.com>
Gerrit-Reviewer: kokoro <noreply+kok...@google.com>
Gerrit-CC: Luming Wang <wlm199...@126.com>
Gerrit-MessageType: merged
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