* bug fixes

* reduced memory footprint for IPI virtualization on Intel processors
 * asynchronous teardown support (Linux only)
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Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging

* bug fixes
* reduced memory footprint for IPI virtualization on Intel processors
* asynchronous teardown support (Linux only)

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# gpg: Signature made Wed 02 Nov 2022 07:40:25 EDT
# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
# gpg:                issuer "pbonzini@redhat.com"
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full]
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* tag 'for-upstream' of https://gitlab.com/bonzini/qemu:
  target/i386: Fix test for paging enabled
  util/log: Close per-thread log file on thread termination
  target/i386: Set maximum APIC ID to KVM prior to vCPU creation
  os-posix: asynchronous teardown for shutdown on Linux
  target/i386: Fix calculation of LOCK NEG eflags

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

util/async-teardown.c

@@ -0,0 +1,150 @@
+/*
+ * Asynchronous teardown
+ *
+ * Copyright IBM, Corp. 2022
+ *
+ * Authors:
+ *  Claudio Imbrenda <imbrenda@linux.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or (at your
+ * option) any later version.  See the COPYING file in the top-level directory.
+ *
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <sys/prctl.h>
+#include <signal.h>
+#include <sched.h>
+#include <unistd.h>
+
+#include "qemu/osdep.h"
+#include "qemu/async-teardown.h"
+
+#ifdef _SC_THREAD_STACK_MIN
+#define CLONE_STACK_SIZE sysconf(_SC_THREAD_STACK_MIN)
+#else
+#define CLONE_STACK_SIZE 16384
+#endif
+
+static pid_t the_ppid;
+
+/*
+ * Close all open file descriptors.
+ */
+static void close_all_open_fd(void)
+{
+    struct dirent *de;
+    int fd, dfd;
+    DIR *dir;
+
+#ifdef CONFIG_CLOSE_RANGE
+    int r = close_range(0, ~0U, 0);
+    if (!r) {
+        /* Success, no need to try other ways. */
+        return;
+    }
+#endif
+
+    dir = opendir("/proc/self/fd");
+    if (!dir) {
+        /* If /proc is not mounted, there is nothing that can be done. */
+        return;
+    }
+    /* Avoid closing the directory. */
+    dfd = dirfd(dir);
+
+    for (de = readdir(dir); de; de = readdir(dir)) {
+        fd = atoi(de->d_name);
+        if (fd != dfd) {
+            close(fd);
+        }
+    }
+    closedir(dir);
+}
+
+static void hup_handler(int signal)
+{
+    /* Check every second if this process has been reparented. */
+    while (the_ppid == getppid()) {
+        /* sleep() is safe to use in a signal handler. */
+        sleep(1);
+    }
+
+    /* At this point the parent process has terminated completely. */
+    _exit(0);
+}
+
+static int async_teardown_fn(void *arg)
+{
+    struct sigaction sa = { .sa_handler = hup_handler };
+    sigset_t hup_signal;
+    char name[16];
+
+    /* Set a meaningful name for this process. */
+    snprintf(name, 16, "cleanup/%d", the_ppid);
+    prctl(PR_SET_NAME, (unsigned long)name);
+
+    /*
+     * Close all file descriptors that might have been inherited from the
+     * main qemu process when doing clone, needed to make libvirt happy.
+     * Not using close_range for increased compatibility with older kernels.
+     */
+    close_all_open_fd();
+
+    /* Set up a handler for SIGHUP and unblock SIGHUP. */
+    sigaction(SIGHUP, &sa, NULL);
+    sigemptyset(&hup_signal);
+    sigaddset(&hup_signal, SIGHUP);
+    sigprocmask(SIG_UNBLOCK, &hup_signal, NULL);
+
+    /* Ask to receive SIGHUP when the parent dies. */
+    prctl(PR_SET_PDEATHSIG, SIGHUP);
+
+    /*
+     * Sleep forever, unless the parent process has already terminated. The
+     * only interruption can come from the SIGHUP signal, which in normal
+     * operation is received when the parent process dies.
+     */
+    if (the_ppid == getppid()) {
+        pause();
+    }
+
+    /* At this point the parent process has terminated completely. */
+    _exit(0);
+}
+
+/*
+ * Allocate a new stack of a reasonable size, and return a pointer to its top.
+ */
+static void *new_stack_for_clone(void)
+{
+    size_t stack_size = CLONE_STACK_SIZE;
+    char *stack_ptr;
+
+    /* Allocate a new stack and get a pointer to its top. */
+    stack_ptr = qemu_alloc_stack(&stack_size);
+#if !defined(HOST_HPPA)
+    /* The top is at the end of the area, except on HPPA. */
+    stack_ptr += stack_size;
+#endif
+
+    return stack_ptr;
+}
+
+/*
+ * Block all signals, start (clone) a new process sharing the address space
+ * with qemu (CLONE_VM), then restore signals.
+ */
+void init_async_teardown(void)
+{
+    sigset_t all_signals, old_signals;
+
+    the_ppid = getpid();
+
+    sigfillset(&all_signals);
+    sigprocmask(SIG_BLOCK, &all_signals, &old_signals);
+    clone(async_teardown_fn, new_stack_for_clone(), CLONE_VM, NULL);
+    sigprocmask(SIG_SETMASK, &old_signals, NULL);
+}

util/log.c

@@ -42,6 +42,7 @@ static QemuMutex global_mutex;
 static char *global_filename;
 static FILE *global_file;
 static __thread FILE *thread_file;
+static __thread Notifier qemu_log_thread_cleanup_notifier;
 
 int qemu_loglevel;
 static bool log_append;
@@ -77,6 +78,12 @@ static int log_thread_id(void)
 #endif
 }
 
+static void qemu_log_thread_cleanup(Notifier *n, void *unused)
+{
+    fclose(thread_file);
+    thread_file = NULL;
+}
+
 /* Lock/unlock output. */
 
 FILE *qemu_log_trylock(void)
@@ -93,6 +100,8 @@ FILE *qemu_log_trylock(void)
                 return NULL;
             }
             thread_file = logfile;
+            qemu_log_thread_cleanup_notifier.notify = qemu_log_thread_cleanup;
+            qemu_thread_atexit_add(&qemu_log_thread_cleanup_notifier);
         } else {
             rcu_read_lock();
             /*

util/meson.build

@@ -3,6 +3,7 @@ util_ss.add(files('thread-context.c'), numa)
 if not config_host_data.get('CONFIG_ATOMIC64')
   util_ss.add(files('atomic64.c'))
 endif
+util_ss.add(when: 'CONFIG_LINUX', if_true: files('async-teardown.c'))
 util_ss.add(when: 'CONFIG_POSIX', if_true: files('aio-posix.c'))
 util_ss.add(when: 'CONFIG_POSIX', if_true: files('fdmon-poll.c'))
 if config_host_data.get('CONFIG_EPOLL_CREATE1')