[pve-devel] [RFC pve-qemu] Add systemd journal logging patch

[Stefan Reiter]

Prints QEMU errors that occur *after* the "-daemonize" fork to the
systemd journal, instead of pushing them into /dev/null like before.

Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
---

Useful for debugging rust panics for example. I'm sure there's other ways to go
about this (log files? pass the journal fd from outside? pipe it into the
journal somehow?) but this one seems simple enough, though it of course requires
linking QEMU against libsystemd.

@dietmar: is this similar to what you had in mind?

 debian/control                                |  1 +
 ...ct-stderr-to-journal-when-daemonized.patch | 50 +++++++++++++++++++
 debian/patches/series                         |  1 +
 3 files changed, 52 insertions(+)
 create mode 100644 debian/patches/pve/0052-PVE-redirect-stderr-to-journal-when-daemonized.patch

diff --git a/debian/control b/debian/control
index caceabb..e6d935d 100644
--- a/debian/control
+++ b/debian/control
@@ -25,6 +25,7 @@ Build-Depends: autotools-dev,
                libseccomp-dev,
                libspice-protocol-dev (>= 0.12.14~),
                libspice-server-dev (>= 0.14.0~),
+               libsystemd-dev,
                libusb-1.0-0-dev (>= 1.0.17-1),
                libusbredirparser-dev (>= 0.6-2),
                python3-minimal,
diff --git a/debian/patches/pve/0052-PVE-redirect-stderr-to-journal-when-daemonized.patch b/debian/patches/pve/0052-PVE-redirect-stderr-to-journal-when-daemonized.patch
new file mode 100644
index 0000000..f73de53
--- /dev/null
+++ b/debian/patches/pve/0052-PVE-redirect-stderr-to-journal-when-daemonized.patch
@@ -0,0 +1,50 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Stefan Reiter <s.reiter at proxmox.com>
+Date: Tue, 30 Jun 2020 13:10:10 +0200
+Subject: [PATCH] PVE: redirect stderr to journal when daemonized
+
+QEMU uses the logging for error messages usually, so LOG_ERR is most
+fitting.
+---
+ Makefile.objs | 1 +
+ os-posix.c    | 7 +++++--
+ 2 files changed, 6 insertions(+), 2 deletions(-)
+
+diff --git a/Makefile.objs b/Makefile.objs
+index b7d58e592e..105f23bff7 100644
+--- a/Makefile.objs
++++ b/Makefile.objs
+@@ -55,6 +55,7 @@ common-obj-y += net/
+ common-obj-y += qdev-monitor.o
+ common-obj-$(CONFIG_WIN32) += os-win32.o
+ common-obj-$(CONFIG_POSIX) += os-posix.o
++os-posix.o-libs := -lsystemd
+ 
+ common-obj-$(CONFIG_LINUX) += fsdev/
+ 
+diff --git a/os-posix.c b/os-posix.c
+index 3cd52e1e70..ab4d052c62 100644
+--- a/os-posix.c
++++ b/os-posix.c
+@@ -28,6 +28,8 @@
+ #include <pwd.h>
+ #include <grp.h>
+ #include <libgen.h>
++#include <systemd/sd-journal.h>
++#include <syslog.h>
+ 
+ #include "qemu-common.h"
+ /* Needed early for CONFIG_BSD etc. */
+@@ -309,9 +311,10 @@ void os_setup_post(void)
+ 
+         dup2(fd, 0);
+         dup2(fd, 1);
+-        /* In case -D is given do not redirect stderr to /dev/null */
++        /* In case -D is given do not redirect stderr to journal */
+         if (!qemu_logfile) {
+-            dup2(fd, 2);
++            int journal_fd = sd_journal_stream_fd("QEMU", LOG_ERR, 0);
++            dup2(journal_fd, 2);
+         }
+ 
+         close(fd);
diff --git a/debian/patches/series b/debian/patches/series
index 5d6a5d6..e658c1a 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -50,3 +50,4 @@ pve/0048-savevm-async-add-debug-timing-prints.patch
 pve/0049-Add-some-qemu_vfree-statements-to-prevent-memory-lea.patch
 pve/0050-Fix-backup-for-not-64k-aligned-storages.patch
 pve/0051-PVE-Backup-Add-dirty-bitmap-tracking-for-incremental.patch
+pve/0052-PVE-redirect-stderr-to-journal-when-daemonized.patch
-- 
2.20.1