The Xen mapcache is able to create long term mappings, they are called
"locked" mappings. The third parameter of the xen_map_cache call
specifies if a mapping is a "locked" mapping.

>From the QEMU point of view there are two kinds of long term mappings:

[a] device memory mappings, such as option roms and video memory
[b] dma mappings, created by dma_memory_map & friends

After certain operations, ballooning a VM in particular, Xen asks QEMU
kindly to destroy all mappings. However, certainly [a] mappings are
present and cannot be removed. That's not a problem as they are not
affected by balloonning. The *real* problem is that if there are any
mappings of type [b], any outstanding dma operations could fail. This is
a known shortcoming. In other words, when Xen asks QEMU to destroy all
mappings, it is an error if any [b] mappings exist.

However today we have no way of distinguishing [a] from [b]. Because of
that, we cannot even print a decent warning.

This patch introduces a new "dma" bool field to MapCacheRev entires, to
remember if a given mapping is for dma or is a long term device memory
mapping. When xen_invalidate_map_cache is called, we print a warning if
any [b] mappings exist. We ignore [a] mappings.

Mappings created by qemu_map_ram_ptr are assumed to be [a], while
mappings created by address_space_map->qemu_ram_ptr_length are assumed
to be [b].

The goal of the patch is to make debugging and system understanding
easier.

Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
---
 exec.c                        |  8 ++++----
 hw/i386/xen/xen-mapcache.c    | 15 ++++++++++-----
 include/sysemu/xen-mapcache.h |  5 +++--
 3 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/exec.c b/exec.c
index eac6085..85769e1 100644
--- a/exec.c
+++ b/exec.c
@@ -2084,10 +2084,10 @@ void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr)
          * In that case just map until the end of the page.
          */
         if (block->offset == 0) {
-            return xen_map_cache(addr, 0, 0);
+            return xen_map_cache(addr, 0, 0, false);
         }
 
-        block->host = xen_map_cache(block->offset, block->max_length, 1);
+        block->host = xen_map_cache(block->offset, block->max_length, 1, false);
     }
     return ramblock_ptr(block, addr);
 }
@@ -2117,10 +2117,10 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, ram_addr_t addr,
          * In that case just map the requested area.
          */
         if (block->offset == 0) {
-            return xen_map_cache(addr, *size, 1);
+            return xen_map_cache(addr, *size, 1, true);
         }
 
-        block->host = xen_map_cache(block->offset, block->max_length, 1);
+        block->host = xen_map_cache(block->offset, block->max_length, 1, true);
     }
 
     return ramblock_ptr(block, addr);
diff --git a/hw/i386/xen/xen-mapcache.c b/hw/i386/xen/xen-mapcache.c
index 31debdf..e60156c 100644
--- a/hw/i386/xen/xen-mapcache.c
+++ b/hw/i386/xen/xen-mapcache.c
@@ -62,6 +62,7 @@ typedef struct MapCacheRev {
     hwaddr paddr_index;
     hwaddr size;
     QTAILQ_ENTRY(MapCacheRev) next;
+    bool dma;
 } MapCacheRev;
 
 typedef struct MapCache {
@@ -202,7 +203,7 @@ static void xen_remap_bucket(MapCacheEntry *entry,
 }
 
 static uint8_t *xen_map_cache_unlocked(hwaddr phys_addr, hwaddr size,
-                                       uint8_t lock)
+                                       uint8_t lock, bool dma)
 {
     MapCacheEntry *entry, *pentry = NULL;
     hwaddr address_index;
@@ -289,6 +290,7 @@ tryagain:
     if (lock) {
         MapCacheRev *reventry = g_malloc0(sizeof(MapCacheRev));
         entry->lock++;
+        reventry->dma = dma;
         reventry->vaddr_req = mapcache->last_entry->vaddr_base + address_offset;
         reventry->paddr_index = mapcache->last_entry->paddr_index;
         reventry->size = entry->size;
@@ -300,12 +302,12 @@ tryagain:
 }
 
 uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size,
-                       uint8_t lock)
+                       uint8_t lock, bool dma)
 {
     uint8_t *p;
 
     mapcache_lock();
-    p = xen_map_cache_unlocked(phys_addr, size, lock);
+    p = xen_map_cache_unlocked(phys_addr, size, lock, dma);
     mapcache_unlock();
     return p;
 }
@@ -426,8 +428,11 @@ void xen_invalidate_map_cache(void)
     mapcache_lock();
 
     QTAILQ_FOREACH(reventry, &mapcache->locked_entries, next) {
-        DPRINTF("There should be no locked mappings at this time, "
-                "but "TARGET_FMT_plx" -> %p is present\n",
+        if (!reventry->dma) {
+            continue;
+        }
+        fprintf(stderr, "Locked DMA mapping while invalidating mapcache!"
+                " "TARGET_FMT_plx" -> %p is present\n",
                 reventry->paddr_index, reventry->vaddr_req);
     }
 
diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h
index b8c93b9..01daaad 100644
--- a/include/sysemu/xen-mapcache.h
+++ b/include/sysemu/xen-mapcache.h
@@ -17,7 +17,7 @@ typedef hwaddr (*phys_offset_to_gaddr_t)(hwaddr start_addr,
 void xen_map_cache_init(phys_offset_to_gaddr_t f,
                         void *opaque);
 uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size,
-                       uint8_t lock);
+                       uint8_t lock, bool dma);
 ram_addr_t xen_ram_addr_from_mapcache(void *ptr);
 void xen_invalidate_map_cache_entry(uint8_t *buffer);
 void xen_invalidate_map_cache(void);
@@ -31,7 +31,8 @@ static inline void xen_map_cache_init(phys_offset_to_gaddr_t f,
 
 static inline uint8_t *xen_map_cache(hwaddr phys_addr,
                                      hwaddr size,
-                                     uint8_t lock)
+                                     uint8_t lock,
+                                     bool dma)
 {
     abort();
 }
-- 
1.9.1

From: Anthony PERARD <anthony.perard@citrix.com>

QEMU does not depends on libxencall, it was added because it was a
missing link dependency of libxendevicemodel, but now the later should
be built properly.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
---
 configure | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure b/configure
index 57b5ae6..139638e 100755
--- a/configure
+++ b/configure
@@ -2015,7 +2015,7 @@ if test "$xen" != "no" ; then
   else
 
     xen_libs="-lxenstore -lxenctrl -lxenguest"
-    xen_stable_libs="-lxencall -lxenforeignmemory -lxengnttab -lxenevtchn"
+    xen_stable_libs="-lxenforeignmemory -lxengnttab -lxenevtchn"
 
     # First we test whether Xen headers and libraries are available.
     # If no, we are done and there is no Xen support.
-- 
1.9.1

CID: 1374836

Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
CC: anthony.perard@citrix.com
CC: groug@kaod.org
CC: aneesh.kumar@linux.vnet.ibm.com
---
 hw/9pfs/xen-9p-backend.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 9c7f41a..a1fdede 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -332,12 +332,14 @@ static int xen_9pfs_connect(struct XenDevice *xendev)
         str = g_strdup_printf("ring-ref%u", i);
         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
                                  &xen_9pdev->rings[i].ref) == -1) {
+            g_free(str);
             goto out;
         }
         g_free(str);
         str = g_strdup_printf("event-channel-%u", i);
         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
                                  &xen_9pdev->rings[i].evtchn) == -1) {
+            g_free(str);
             goto out;
         }
         g_free(str);
-- 
1.9.1

Use the common utility function, which contains checks on return values
and first calls F_GETFD as recommended by POSIX.1-2001, instead of
manually calling fcntl.

CID: 1374831

Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
CC: anthony.perard@citrix.com
CC: groug@kaod.org
CC: aneesh.kumar@linux.vnet.ibm.com
CC: Eric Blake <eblake@redhat.com>
---
 hw/9pfs/xen-9p-backend.c | 2 +-
 hw/xen/xen_backend.c     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index a1fdede..5df97c9 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -380,7 +380,7 @@ static int xen_9pfs_connect(struct XenDevice *xendev)
         if (xen_9pdev->rings[i].evtchndev == NULL) {
             goto out;
         }
-        fcntl(xenevtchn_fd(xen_9pdev->rings[i].evtchndev), F_SETFD, FD_CLOEXEC);
+        qemu_set_cloexec(xenevtchn_fd(xen_9pdev->rings[i].evtchndev));
         xen_9pdev->rings[i].local_port = xenevtchn_bind_interdomain
                                             (xen_9pdev->rings[i].evtchndev,
                                              xendev->dom,
diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
index c85f163..2cac47d 100644
--- a/hw/xen/xen_backend.c
+++ b/hw/xen/xen_backend.c
@@ -147,7 +147,7 @@ static struct XenDevice *xen_be_get_xendev(const char *type, int dom, int dev,
         qdev_unplug(DEVICE(xendev), NULL);
         return NULL;
     }
-    fcntl(xenevtchn_fd(xendev->evtchndev), F_SETFD, FD_CLOEXEC);
+    qemu_set_cloexec(xenevtchn_fd(xendev->evtchndev));
 
     if (ops->flags & DEVOPS_FLAG_NEED_GNTDEV) {
         xendev->gnttabdev = xengnttab_open(NULL, 0);
-- 
1.9.1