Introduce qemu_madvise()

vl.c has a Sun-specific hack to supply a prototype for madvise(),
but the call site has apparently moved to arch_init.c.

Haiku doesn't implement madvise() in favor of posix_madvise().
OpenBSD and Solaris 10 don't implement posix_madvise() but madvise().
MinGW implements neither.

Check for madvise() and posix_madvise() in configure and supply qemu_madvise()
as wrapper. Prefer madvise() over posix_madvise() due to flag availability.
Convert all callers to use qemu_madvise() and QEMU_MADV_*.

Note that on Solaris the warning is fixed by moving the madvise() prototype,
not by qemu_madvise() itself. It helps with porting though, and it simplifies
most call sites.

v7 -> v8:
* Some versions of MinGW have no sys/mman.h header. Reported by Blue Swirl.

v6 -> v7:
* Adopt madvise() rather than posix_madvise() semantics for returning errors.
* Use EINVAL in place of ENOTSUP.

v5 -> v6:
* Replace two leftover instances of POSIX_MADV_NORMAL with QEMU_MADV_INVALID.
  Spotted by Blue Swirl.

v4 -> v5:
* Introduce QEMU_MADV_INVALID, suggested by Alexander Graf.
  Note that this relies on -1 not being a valid advice value.

v3 -> v4:
* Eliminate #ifdefs at qemu_advise() call sites. Requested by Blue Swirl.
  This will currently break the check in kvm-all.c by calling madvise() with
  a supported flag, which will not fail. Ideas/patches welcome.

v2 -> v3:
* Reuse the *_MADV_* defines for QEMU_MADV_*. Suggested by Alexander Graf.
* Add configure check for madvise(), too.
  Add defines to Makefile, not QEMU_CFLAGS.
  Convert all callers, untested. Suggested by Blue Swirl.
* Keep Solaris' madvise() prototype around. Pointed out by Alexander Graf.
* Display configure check results.

v1 -> v2:
* Don't rely on posix_madvise() availability, add qemu_madvise().
  Suggested by Blue Swirl.

Signed-off-by: Andreas Färber <afaerber@opensolaris.org>
Cc: Blue Swirl <blauwirbel@gmail.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

arch_init.c

@@ -396,7 +396,7 @@ int ram_load(QEMUFile *f, void *opaque, int version_id)
 #ifndef _WIN32
             if (ch == 0 &&
                 (!kvm_enabled() || kvm_has_sync_mmu())) {
-                madvise(host, TARGET_PAGE_SIZE, MADV_DONTNEED);
+                qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED);
             }
 #endif
         } else if (flags & RAM_SAVE_FLAG_PAGE) {

configure

@@ -2071,6 +2071,31 @@ if compile_prog "" "" ; then
     fdatasync=yes
 fi
 
+##########################################
+# check if we have madvise
+
+madvise=no
+cat > $TMPC << EOF
+#include <sys/types.h>
+#include <sys/mman.h>
+int main(void) { return madvise(NULL, 0, MADV_DONTNEED); }
+EOF
+if compile_prog "" "" ; then
+    madvise=yes
+fi
+
+##########################################
+# check if we have posix_madvise
+
+posix_madvise=no
+cat > $TMPC << EOF
+#include <sys/mman.h>
+int main(void) { return posix_madvise(NULL, 0, POSIX_MADV_DONTNEED); }
+EOF
+if compile_prog "" "" ; then
+    posix_madvise=yes
+fi
+
 ##########################################
 # check if trace backend exists
 
@@ -2238,6 +2263,8 @@ echo "KVM support       $kvm"
 echo "fdt support       $fdt"
 echo "preadv support    $preadv"
 echo "fdatasync         $fdatasync"
+echo "madvise           $madvise"
+echo "posix_madvise     $posix_madvise"
 echo "uuid support      $uuid"
 echo "vhost-net support $vhost_net"
 echo "Trace backend     $trace_backend"
@@ -2478,6 +2505,12 @@ fi
 if test "$fdatasync" = "yes" ; then
   echo "CONFIG_FDATASYNC=y" >> $config_host_mak
 fi
+if test "$madvise" = "yes" ; then
+  echo "CONFIG_MADVISE=y" >> $config_host_mak
+fi
+if test "$posix_madvise" = "yes" ; then
+  echo "CONFIG_POSIX_MADVISE=y" >> $config_host_mak
+fi
 
 # XXX: suppress that
 if [ "$bsd" = "yes" ] ; then

exec.c

@@ -2841,9 +2841,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState *dev, const char *name,
             new_block->host = file_ram_alloc(new_block, size, mem_path);
             if (!new_block->host) {
                 new_block->host = qemu_vmalloc(size);
-#ifdef MADV_MERGEABLE
+                qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE);
-                madvise(new_block->host, size, MADV_MERGEABLE);
-#endif
             }
 #else
             fprintf(stderr, "-mem-path option unsupported\n");
@@ -2858,9 +2856,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState *dev, const char *name,
 #else
             new_block->host = qemu_vmalloc(size);
 #endif
-#ifdef MADV_MERGEABLE
+            qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE);
-            madvise(new_block->host, size, MADV_MERGEABLE);
-#endif
         }
     }
 

hw/virtio-balloon.c

@@ -51,8 +51,8 @@ static void balloon_page(void *addr, int deflate)
 {
 #if defined(__linux__)
     if (!kvm_enabled() || kvm_has_sync_mmu())
-        madvise(addr, TARGET_PAGE_SIZE,
+        qemu_madvise(addr, TARGET_PAGE_SIZE,
-                deflate ? MADV_WILLNEED : MADV_DONTNEED);
+                deflate ? QEMU_MADV_WILLNEED : QEMU_MADV_DONTNEED);
 #endif
 }
 

kvm-all.c

@@ -1031,18 +1031,14 @@ int kvm_has_xcrs(void)
 void kvm_setup_guest_memory(void *start, size_t size)
 {
     if (!kvm_has_sync_mmu()) {
-#ifdef MADV_DONTFORK
+        int ret = qemu_madvise(start, size, QEMU_MADV_DONTFORK);
-        int ret = madvise(start, size, MADV_DONTFORK);
 
         if (ret) {
-            perror("madvice");
+            perror("qemu_madvise");
+            fprintf(stderr,
+                    "Need MADV_DONTFORK in absence of synchronous KVM MMU\n");
             exit(1);
         }
-#else
-        fprintf(stderr,
-                "Need MADV_DONTFORK in absence of synchronous KVM MMU\n");
-        exit(1);
-#endif
     }
 }
 

osdep.c

@@ -32,9 +32,16 @@
 /* Needed early for CONFIG_BSD etc. */
 #include "config-host.h"
 
+#if defined(CONFIG_MADVISE) || defined(CONFIG_POSIX_MADVISE)
+#include <sys/mman.h>
+#endif
+
 #ifdef CONFIG_SOLARIS
 #include <sys/types.h>
 #include <sys/statvfs.h>
+/* See MySQL bug #7156 (http://bugs.mysql.com/bug.php?id=7156) for
+   discussion about Solaris header problems */
+extern int madvise(caddr_t, size_t, int);
 #endif
 
 #ifdef CONFIG_EVENTFD
@@ -139,6 +146,22 @@ void qemu_vfree(void *ptr)
 
 #endif
 
+int qemu_madvise(void *addr, size_t len, int advice)
+{
+    if (advice == QEMU_MADV_INVALID) {
+        errno = EINVAL;
+        return -1;
+    }
+#if defined(CONFIG_MADVISE)
+    return madvise(addr, len, advice);
+#elif defined(CONFIG_POSIX_MADVISE)
+    return posix_madvise(addr, len, advice);
+#else
+    errno = EINVAL;
+    return -1;
+#endif
+}
+
 int qemu_create_pidfile(const char *filename)
 {
     char buffer[128];

osdep.h

@@ -90,6 +90,41 @@ void *qemu_memalign(size_t alignment, size_t size);
 void *qemu_vmalloc(size_t size);
 void qemu_vfree(void *ptr);
 
+#define QEMU_MADV_INVALID -1
+
+#if defined(CONFIG_MADVISE)
+
+#define QEMU_MADV_WILLNEED  MADV_WILLNEED
+#define QEMU_MADV_DONTNEED  MADV_DONTNEED
+#ifdef MADV_DONTFORK
+#define QEMU_MADV_DONTFORK  MADV_DONTFORK
+#else
+#define QEMU_MADV_DONTFORK  QEMU_MADV_INVALID
+#endif
+#ifdef MADV_MERGEABLE
+#define QEMU_MADV_MERGEABLE MADV_MERGEABLE
+#else
+#define QEMU_MADV_MERGEABLE QEMU_MADV_INVALID
+#endif
+
+#elif defined(CONFIG_POSIX_MADVISE)
+
+#define QEMU_MADV_WILLNEED  POSIX_MADV_WILLNEED
+#define QEMU_MADV_DONTNEED  POSIX_MADV_DONTNEED
+#define QEMU_MADV_DONTFORK  QEMU_MADV_INVALID
+#define QEMU_MADV_MERGEABLE QEMU_MADV_INVALID
+
+#else /* no-op */
+
+#define QEMU_MADV_WILLNEED  QEMU_MADV_INVALID
+#define QEMU_MADV_DONTNEED  QEMU_MADV_INVALID
+#define QEMU_MADV_DONTFORK  QEMU_MADV_INVALID
+#define QEMU_MADV_MERGEABLE QEMU_MADV_INVALID
+
+#endif
+
+int qemu_madvise(void *addr, size_t len, int advice);
+
 int qemu_create_pidfile(const char *filename);
 
 #ifdef _WIN32

vl.c

@@ -80,9 +80,6 @@
 #include <net/if.h>
 #include <syslog.h>
 #include <stropts.h>
-/* See MySQL bug #7156 (http://bugs.mysql.com/bug.php?id=7156) for
-   discussion about Solaris header problems */
-extern int madvise(caddr_t, size_t, int);
 #endif
 #endif
 #endif