diff --git a/test/benchmark/iperf3/tcp_virtio_bw/host.sh b/test/benchmark/iperf3/tcp_virtio_bw/host.sh
index 9c61a2fb..5f8912bf 100755
--- a/test/benchmark/iperf3/tcp_virtio_bw/host.sh
+++ b/test/benchmark/iperf3/tcp_virtio_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/memcached/t16_conc64_window10k/host.sh b/test/benchmark/memcached/t16_conc64_window10k/host.sh
index 681eb92d..7caf45af 100644
--- a/test/benchmark/memcached/t16_conc64_window10k/host.sh
+++ b/test/benchmark/memcached/t16_conc64_window10k/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/memcached/t8_conc32_window10k/host.sh b/test/benchmark/memcached/t8_conc32_window10k/host.sh
index dab79035..411d5aea 100644
--- a/test/benchmark/memcached/t8_conc32_window10k/host.sh
+++ b/test/benchmark/memcached/t8_conc32_window10k/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/memcached/t8_conc32_window20k/host.sh b/test/benchmark/memcached/t8_conc32_window20k/host.sh
index 9aa37551..9cd6262b 100644
--- a/test/benchmark/memcached/t8_conc32_window20k/host.sh
+++ b/test/benchmark/memcached/t8_conc32_window20k/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/nginx/http_file16KB_bw/host.sh b/test/benchmark/nginx/http_file16KB_bw/host.sh
index ff6d4428..74ece790 100644
--- a/test/benchmark/nginx/http_file16KB_bw/host.sh
+++ b/test/benchmark/nginx/http_file16KB_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/nginx/http_file32KB_bw/host.sh b/test/benchmark/nginx/http_file32KB_bw/host.sh
index aabd10e5..e595922c 100644
--- a/test/benchmark/nginx/http_file32KB_bw/host.sh
+++ b/test/benchmark/nginx/http_file32KB_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/nginx/http_file4KB_bw/host.sh b/test/benchmark/nginx/http_file4KB_bw/host.sh
index 7cf609bd..1f054062 100644
--- a/test/benchmark/nginx/http_file4KB_bw/host.sh
+++ b/test/benchmark/nginx/http_file4KB_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/nginx/http_file64KB_bw/host.sh b/test/benchmark/nginx/http_file64KB_bw/host.sh
index ec9e945e..a629162b 100644
--- a/test/benchmark/nginx/http_file64KB_bw/host.sh
+++ b/test/benchmark/nginx/http_file64KB_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/nginx/http_file8KB_bw/host.sh b/test/benchmark/nginx/http_file8KB_bw/host.sh
index 5417bba8..a1c713a7 100644
--- a/test/benchmark/nginx/http_file8KB_bw/host.sh
+++ b/test/benchmark/nginx/http_file8KB_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/nginx/http_req10k_conc1_bw/host.sh b/test/benchmark/nginx/http_req10k_conc1_bw/host.sh
index f5bd3803..19fbd55b 100755
--- a/test/benchmark/nginx/http_req10k_conc1_bw/host.sh
+++ b/test/benchmark/nginx/http_req10k_conc1_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/nginx/http_req10k_conc20_bw/host.sh b/test/benchmark/nginx/http_req10k_conc20_bw/host.sh
index a3a7de67..2d81bbc4 100755
--- a/test/benchmark/nginx/http_req10k_conc20_bw/host.sh
+++ b/test/benchmark/nginx/http_req10k_conc20_bw/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/redis/get_100k_conc20_rps/host.sh b/test/benchmark/redis/get_100k_conc20_rps/host.sh
index 753aab37..32eb3cb8 100755
--- a/test/benchmark/redis/get_100k_conc20_rps/host.sh
+++ b/test/benchmark/redis/get_100k_conc20_rps/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/redis/ping_inline_100k_conc20_rps/host.sh b/test/benchmark/redis/ping_inline_100k_conc20_rps/host.sh
index 4e2d124e..b67b7499 100755
--- a/test/benchmark/redis/ping_inline_100k_conc20_rps/host.sh
+++ b/test/benchmark/redis/ping_inline_100k_conc20_rps/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/redis/ping_mbulk_100k_conc20_rps/host.sh b/test/benchmark/redis/ping_mbulk_100k_conc20_rps/host.sh
index af651378..a8c7d9a1 100755
--- a/test/benchmark/redis/ping_mbulk_100k_conc20_rps/host.sh
+++ b/test/benchmark/redis/ping_mbulk_100k_conc20_rps/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit
diff --git a/test/benchmark/redis/set_100k_conc20_rps/host.sh b/test/benchmark/redis/set_100k_conc20_rps/host.sh
index 84f5878c..e0a83410 100755
--- a/test/benchmark/redis/set_100k_conc20_rps/host.sh
+++ b/test/benchmark/redis/set_100k_conc20_rps/host.sh
@@ -7,7 +7,8 @@ set -e
 # Function to stop the guest VM
 stop_guest() {
     echo "Stopping guest VM..."
-    pgrep qemu | xargs kill
+    # `-r` means if there's no qemu, the kill won't be executed
+    pgrep qemu | xargs -r kill
 }
 
 # Trap EXIT signal to ensure guest VM is stopped on script exit