qemu_init: increase NOFILE soft limit on POSIX

In many configurations, e.g. multiple vNICs with multiple queues or
with many Ceph OSDs, the default soft limit of 1024 is not enough.
QEMU is supposed to work fine with file descriptors >= 1024 and does
not use select() on POSIX. Bump the soft limit to the allowed hard
limit to avoid issues with the aforementioned configurations.

Of course the limit could be raised from the outside, but the man page
of systemd.exec states about 'LimitNOFILE=':

> Don't use.
> [...]
> Typically applications should increase their soft limit to the hard
> limit on their own, if they are OK with working with file
> descriptors above 1023,

If the soft limit is already the same as the hard limit, avoid the
superfluous setrlimit call. This can avoid a warning with a strict
seccomp filter blocking setrlimit if NOFILE was already raised before
executing QEMU.

Buglink: https://bugzilla.proxmox.com/show_bug.cgi?id=4507
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h
index dff32ae185a613ef54ec794bac656481b027991c..b881ac6c6f743038039453007c355be68c0e5514 100644 (file)
--- a/include/sysemu/os-posix.h
+++ b/include/sysemu/os-posix.h
@@ -51,6 +51,7 @@ bool is_daemonized(void);
 void os_daemonize(void);
 bool os_set_runas(const char *user_id);
 void os_set_chroot(const char *path);
+void os_setup_limits(void);
 void os_setup_post(void);
 int os_mlock(void);
 

diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h
index 1047d260cbd4ff618ad407e69567b855048ac8c0..b82a5d3ad93c4538bfae173e94a8e7f432645f34 100644 (file)
--- a/include/sysemu/os-win32.h
+++ b/include/sysemu/os-win32.h
@@ -128,6 +128,11 @@ static inline int os_mlock(void)
     return -ENOSYS;
 }
 
+static inline void os_setup_limits(void)
+{
+    return;
+}
+
 #define fsync _commit
 
 #if !defined(lseek)

diff --git a/os-posix.c b/os-posix.c
index 52ef6990ff9d4c4e2cd52b6f6a820cdbb8efb9fb..a4284e2c07bb7f276dfb7f3cfdec133fb76ff4cd 100644 (file)
--- a/os-posix.c
+++ b/os-posix.c
@@ -24,6 +24,7 @@
  */
 
 #include "qemu/osdep.h"
+#include <sys/resource.h>
 #include <sys/wait.h>
 #include <pwd.h>
 #include <grp.h>
@@ -256,6 +257,27 @@ void os_daemonize(void)
     }
 }
 
+void os_setup_limits(void)
+{
+    struct rlimit nofile;
+
+    if (getrlimit(RLIMIT_NOFILE, &nofile) < 0) {
+        warn_report("unable to query NOFILE limit: %s", strerror(errno));
+        return;
+    }
+
+    if (nofile.rlim_cur == nofile.rlim_max) {
+        return;
+    }
+
+    nofile.rlim_cur = nofile.rlim_max;
+
+    if (setrlimit(RLIMIT_NOFILE, &nofile) < 0) {
+        warn_report("unable to set NOFILE limit: %s", strerror(errno));
+        return;
+    }
+}
+
 void os_setup_post(void)
 {
     int fd = 0;

diff --git a/system/vl.c b/system/vl.c
index 2a0bd08ff19217e5f1c1c393275bc6c3bb8bf251..95cd2d91c450c735642ea04c396fe632fc03f112 100644 (file)
--- a/system/vl.c
+++ b/system/vl.c
@@ -2778,6 +2778,8 @@ void qemu_init(int argc, char **argv)
     error_init(argv[0]);
     qemu_init_exec_dir(argv[0]);
 
+    os_setup_limits();
+
     qemu_init_arch_modules();
 
     qemu_init_subsystems();