From e7476647385a9b613ec0e14bd2b4a4e57d848c64 Mon Sep 17 00:00:00 2001
From: Jonathan Lebon <jonathan@jlebon.com>
Date: Mon, 6 May 2024 14:04:38 -0400
Subject: [PATCH 1/2] Revert "cmdlib.sh: go back to using `tail -F` for command
 output"

This reverts commit 79b15c89d57a4b97334c70881b036aee3462f1e4.

I found a workaround for the issue that prompted that commit. See next
commit.
---
 src/cmdlib.sh | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/src/cmdlib.sh b/src/cmdlib.sh
index e477a628ad..123d560cd6 100755
--- a/src/cmdlib.sh
+++ b/src/cmdlib.sh
@@ -733,9 +733,6 @@ runvm() {
     # and include all GPG keys
     find /etc/pki/rpm-gpg/ -type f >> "${vmpreparedir}/hostfiles"
 
-    local cmdoutput
-    cmdoutput=${tmp_builddir}/cmd-output.txt
-
     # the reason we do a heredoc here is so that the var substition takes
     # place immediately instead of having to proxy them through to the VM
     cat > "${vmpreparedir}/init" <<EOF
@@ -755,7 +752,7 @@ rc=0
 # - Use a subshell because otherwise init will use workdir as its cwd and we won't
 #   be able to unmount the virtiofs mount cleanly. This leads to consistency issues.
 if [ -z "${RUNVM_SHELL:-}" ]; then
-  (cd ${workdir}; bash ${tmp_builddir}/cmd.sh |& tee ${cmdoutput}) || rc=\$?
+  (cd ${workdir}; bash ${tmp_builddir}/cmd.sh |& tee /dev/virtio-ports/cosa-cmdout) || rc=\$?
 else
   (cd ${workdir}; bash)
 fi
@@ -789,9 +786,7 @@ EOF
         printf '%q ' "$arg" >> "${tmp_builddir}"/cmd.sh
     done
 
-    touch "${runvm_console}" "${cmdoutput}"
-    setpriv --pdeathsig SIGTERM -- tail -qF "${cmdoutput}" --pid $$ &
-    local tail_pid=$!
+    touch "${runvm_console}"
 
     # There seems to be some false positives in shellcheck
     # https://github.com/koalaman/shellcheck/issues/2217
@@ -826,6 +821,8 @@ EOF
 
     if [ -z "${RUNVM_SHELL:-}" ]; then
         if ! "${kola_args[@]}" -- "${base_qemu_args[@]}" \
+            -device virtserialport,chardev=virtioserial0,name=cosa-cmdout \
+            -chardev stdio,id=virtioserial0 \
             "${qemu_args[@]}"; then
                 cat "${runvm_console}"
                 fatal "Failed to run 'kola qemuexec'"
@@ -845,13 +842,6 @@ EOF
     fi
     rc="$(cat "${rc_file}")"
 
-    # XXX: this is for debugging temporarily
-    if [ -n "${TAIL_SLEEP:-}" ]; then
-        sleep "${TAIL_SLEEP}"
-    fi
-    # cleanup tail before nuking dir containing file it's following
-    kill "$tail_pid"
-
     if [ -n "${cleanup_tmpdir:-}" ]; then
         rm -rf "${tmp_builddir}"
         unset tmp_builddir

From c5adc99aff48e0d55db89e898cd5366bf8ed91e4 Mon Sep 17 00:00:00 2001
From: Jonathan Lebon <jonathan@jlebon.com>
Date: Tue, 7 May 2024 16:12:24 -0400
Subject: [PATCH 2/2] cmdlib.sh: feed `/dev/zero` as qemu stdin

This is a follow-up to 79b15c89d ("cmdlib.sh: go back to using `tail -F`
for command output") which was subsequently reverted.

To summarize, it seems like in QEMU v8.2 (in f40), the guest sometimes
would hang when writing over virtio-serial if the device is hooked up to
the QEMU's stdio.

In testing, removing the `<&-` hack to close QEMU's stdin fixed it for
CoreOS CI but not Prow:

https://github.com/coreos/coreos-assembler/pull/3785#issuecomment-2087342748

I think I've narrowed it down to CoreOS CI (i.e. Jenkins) allocating a
tty and Prow not. When stdin is not a tty, QEMU would immediately gets
EOF if it tries to read anything. I'm not sure exactly what happens, but
I think the virtio-serial hang is linked to this (even though there's no
userspace code in the guest trying to read from the virtio-serial port).

Work around this by explicitly feeding `/dev/zero` to QEMU's stdin.
---
 src/cmdlib.sh                           | 2 +-
 src/secex-genprotimgvm-scripts/runvm.sh | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/cmdlib.sh b/src/cmdlib.sh
index 123d560cd6..c183beaf8d 100755
--- a/src/cmdlib.sh
+++ b/src/cmdlib.sh
@@ -823,7 +823,7 @@ EOF
         if ! "${kola_args[@]}" -- "${base_qemu_args[@]}" \
             -device virtserialport,chardev=virtioserial0,name=cosa-cmdout \
             -chardev stdio,id=virtioserial0 \
-            "${qemu_args[@]}"; then
+            "${qemu_args[@]}" < /dev/zero; then # qemu hangs if it has nothing to read on stdin
                 cat "${runvm_console}"
                 fatal "Failed to run 'kola qemuexec'"
         fi
diff --git a/src/secex-genprotimgvm-scripts/runvm.sh b/src/secex-genprotimgvm-scripts/runvm.sh
index c90a2c604d..a5361a1021 100644
--- a/src/secex-genprotimgvm-scripts/runvm.sh
+++ b/src/secex-genprotimgvm-scripts/runvm.sh
@@ -56,7 +56,7 @@ else
 fi
 
 if ! "${kola_args[@]}" -- "${base_qemu_args[@]}" \
-    "${qemu_args[@]}" <&-; then # the <&- here closes stdin otherwise qemu waits forever
+    "${qemu_args[@]}" < /dev/zero; then # qemu hangs if it has nothing to read on stdin
     cat "${runvm_console}"
     echo "Failed to run 'kola qemuexec'"
     exit 1