[Qemu-devel] [PATCH v3] Introduce qemu_madvise()

["Andreas Färber" <andreas.faerber@web.de>]

From: Andreas Färber <afaerber@opensolaris.org>

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().

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_*. No functional change
except for arch_init.c:ram_load() now potentially falling back to posix_madvise()
or no-op in lack of both.

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.

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>
---
 arch_init.c         |    2 +-
 configure           |   33 +++++++++++++++++++++++++++++++++
 exec.c              |    8 ++++----
 hw/virtio-balloon.c |    4 ++--
 kvm-all.c           |    6 +++---
 osdep.c             |   15 +++++++++++++++
 osdep.h             |   25 +++++++++++++++++++++++++
 vl.c                |    3 ---
 8 files changed, 83 insertions(+), 13 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index e468c0c..a910033 100644
--- a/arch_init.c
+++ b/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) {
diff --git a/configure b/configure
index 4061cb7..86558eb 100755
--- a/configure
+++ b/configure
@@ -2069,6 +2069,31 @@ if compile_prog "" "" ; then
 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
 
 sh "$source_path/tracetool" "--$trace_backend" --check-backend > /dev/null 2> /dev/null
@@ -2226,6 +2251,8 @@ 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     $trace_backend"
@@ -2466,6 +2493,12 @@ fi
 if test "$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
diff --git a/exec.c b/exec.c
index 380dab5..b1fe3e9 100644
--- a/exec.c
+++ b/exec.c
@@ -2841,8 +2841,8 @@ 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
-                madvise(new_block->host, size, MADV_MERGEABLE);
+#ifdef QEMU_MADV_MERGEABLE
+                qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE);
 #endif
             }
 #else
@@ -2858,8 +2858,8 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState *dev, const char *name,
 #else
             new_block->host = qemu_vmalloc(size);
 #endif
-#ifdef MADV_MERGEABLE
-            madvise(new_block->host, size, MADV_MERGEABLE);
+#ifdef QEMU_MADV_MERGEABLE
+            qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE);
 #endif
         }
     }
diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index 9fe3886..1e74674 100644
--- a/hw/virtio-balloon.c
+++ b/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,
-                deflate ? MADV_WILLNEED : MADV_DONTNEED);
+        qemu_madvise(addr, TARGET_PAGE_SIZE,
+                deflate ? QEMU_MADV_WILLNEED : QEMU_MADV_DONTNEED);
 #endif
 }
 
diff --git a/kvm-all.c b/kvm-all.c
index 58b0404..9393419 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1031,11 +1031,11 @@ 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 = madvise(start, size, MADV_DONTFORK);
+#ifdef QEMU_MADV_DONTFORK
+        int ret = qemu_madvise(start, size, QEMU_MADV_DONTFORK);
 
         if (ret) {
-            perror("madvice");
+            perror("qemu_madvise");
             exit(1);
         }
 #else
diff --git a/osdep.c b/osdep.c
index 30426ff..b5e006f 100644
--- a/osdep.c
+++ b/osdep.c
@@ -28,6 +28,7 @@
 #include <errno.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <sys/mman.h>
 
 /* Needed early for CONFIG_BSD etc. */
 #include "config-host.h"
@@ -35,6 +36,9 @@
 #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 +143,17 @@ void qemu_vfree(void *ptr)
 
 #endif
 
+int qemu_madvise(void *addr, size_t len, int advice)
+{
+#if defined(CONFIG_MADVISE)
+    return madvise(addr, len, advice);
+#elif defined(CONFIG_POSIX_MADVISE)
+    return posix_madvise(addr, len, advice);
+#else
+    return -ENOTSUP;
+#endif
+}
+
 int qemu_create_pidfile(const char *filename)
 {
     char buffer[128];
diff --git a/osdep.h b/osdep.h
index 1cdc7e2..552e453 100644
--- a/osdep.h
+++ b/osdep.h
@@ -90,6 +90,31 @@ void *qemu_memalign(size_t alignment, size_t size);
 void *qemu_vmalloc(size_t size);
 void qemu_vfree(void *ptr);
 
+#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
+#endif
+#ifdef MADV_MERGEABLE
+#define QEMU_MADV_MERGEABLE MADV_MERGEABLE
+#endif
+
+#elif defined(CONFIG_POSIX_MADVISE)
+
+#define QEMU_MADV_WILLNEED POSIX_MADV_WILLNEED
+#define QEMU_MADV_DONTNEED POSIX_MADV_DONTNEED
+
+#else /* no-op */
+
+#define QEMU_MADV_WILLNEED (1 << 0)
+#define QEMU_MADV_DONTNEED (2 << 0)
+
+#endif
+
+int qemu_madvise(void *addr, size_t len, int advice);
+
 int qemu_create_pidfile(const char *filename);
 
 #ifdef _WIN32
diff --git a/vl.c b/vl.c
index 3f45aa9..d352d18 100644
--- a/vl.c
+++ b/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
-- 
1.7.2.2