[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 uploaded this change for review. (  
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>
---
M src/dev/virtio/rng.cc
M src/dev/virtio/rng.hh
2 files changed, 21 insertions(+), 7 deletions(-)



diff --git a/src/dev/virtio/rng.cc b/src/dev/virtio/rng.cc
index 50a747c..6123589 100644
--- a/src/dev/virtio/rng.cc
+++ b/src/dev/virtio/rng.cc
@@ -41,6 +41,7 @@
 #include <fcntl.h>
 #include <unistd.h>

+#include "base/random.hh"
 #include "debug/VIORng.hh"
 #include "params/VirtIORng.hh"
 #include "sim/system.hh"
@@ -63,7 +64,7 @@
 VirtIORng::RngQueue::RngQueue(PortProxy &proxy, ByteOrder bo,
     uint16_t size, const std::string &rng_file_path,
     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) {
@@ -97,7 +98,7 @@
             }
             if (!rng_read_success) {
                 // fallback to C++ std rng generator
-                byte = dist(rd_device);
+                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..631e353 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"

@@ -93,9 +91,6 @@
       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: 1
Gerrit-Owner: Hoa Nguyen <hoangu...@ucdavis.edu>
Gerrit-MessageType: newchange
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