From 012a6d20d43aabd8a4f023e63cec8282f9ab66ac Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@kernel.org>
Date: Sat, 31 Jul 2021 15:43:38 -0700
Subject: [PATCH] boot-qemu.sh: Add '--smp' flag

The help text is fairly self explanatory.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 README.txt   |  8 ++++++++
 boot-qemu.sh | 11 +++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/README.txt b/README.txt
index 020efd6..1e21442 100644
--- a/README.txt
+++ b/README.txt
@@ -69,6 +69,14 @@ Optional parameters:
     This can be useful for reproducing certain bugs but booting kernels
     will be much slower.
 
+  -s | --smp:
+    By default, the script does not specify a number of cores for the
+    QEMU machine, which usually means it spawns with only one core.
+    Certain features such as the KCSAN KUnit tests require multiple cores
+    to work so this value will be used for the number of cores for the
+    virtual machine. It can be more than the number of processors on your
+    host machine.
+
   -t | --timeout:
     By default, the timeout command waits 3 minutes before killing the
     QEMU machine. Depending on the power of the host machine, this might
diff --git a/boot-qemu.sh b/boot-qemu.sh
index 0685041..2ab7de6 100755
--- a/boot-qemu.sh
+++ b/boot-qemu.sh
@@ -77,6 +77,10 @@ function parse_parameters() {
                 KVM=false
                 ;;
 
+            -s | --smp)
+                shift && SMP=${1}
+                ;;
+
             -t | --timeout)
                 shift && TIMEOUT=${1}
                 ;;
@@ -187,7 +191,7 @@ function setup_qemu_args() {
             if ${DEBIAN}; then
                 # Booting is so slow without these
                 QEMU_RAM=2G
-                QEMU_ARCH_ARGS+=(-smp 4)
+                QEMU_ARCH_ARGS+=(-smp "${SMP:-4}")
             fi
             QEMU=(qemu-system-aarch64)
             ;;
@@ -277,7 +281,7 @@ function setup_qemu_args() {
                     -cpu host
                     -d "unimp,guest_errors"
                     -enable-kvm
-                    -smp "$(nproc)"
+                    -smp "${SMP:-$(nproc)}"
                 )
             else
                 QEMU_ARCH_ARGS=(-cpu Nehalem)
@@ -342,6 +346,9 @@ function invoke_qemu() {
     fi
     # Removing trailing space for aesthetic purposes
     [[ -n ${APPEND_STRING} ]] && QEMU+=(-append "${APPEND_STRING%* }")
+    if [[ -n ${SMP} ]] && ! echo "${QEMU_ARCH_ARGS[*]}" | grep -q "smp"; then
+        QEMU+=(-smp "${SMP}")
+    fi
     if ${GDB:=false}; then
         while true; do
             if lsof -i:1234 &>/dev/null; then