mem: add share parameter to memory-backend-ram

Currently only file backed memory backend can
be created with a "share" flag in order to allow
sharing guest RAM with other processes in the host.

Add the "share" flag also to RAM Memory Backend
in order to allow remapping parts of the guest RAM
to different host virtual addresses. This is needed
by the RDMA devices in order to remap non-contiguous
QEMU virtual addresses to a contiguous virtual address range.

Moved the "share" flag to the Host Memory base class,
modified phys_mem_alloc to include the new parameter
and a new interface memory_region_init_ram_shared_nomigrate.

There are no functional changes if the new flag is not used.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>

5 files changed, 28 insertions, 4 deletions

diff --git a/include/exec/memory.h b/include/exec/memory.h
index fff9b1d871..15e81113ba 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -436,6 +436,29 @@ void memory_region_init_ram_nomigrate(MemoryRegion *mr,
                                       Error **errp);
 
 /**
+ * memory_region_init_ram_shared_nomigrate:  Initialize RAM memory region.
+ *                                           Accesses into the region will
+ *                                           modify memory directly.
+ *
+ * @mr: the #MemoryRegion to be initialized.
+ * @owner: the object that tracks the region's reference count
+ * @name: Region name, becomes part of RAMBlock name used in migration stream
+ *        must be unique within any device
+ * @size: size of the region.
+ * @share: allow remapping RAM to different addresses
+ * @errp: pointer to Error*, to store an error if it happens.
+ *
+ * Note that this function is similar to memory_region_init_ram_nomigrate.
+ * The only difference is part of the RAM region can be remapped.
+ */
+void memory_region_init_ram_shared_nomigrate(MemoryRegion *mr,
+                                             struct Object *owner,
+                                             const char *name,
+                                             uint64_t size,
+                                             bool share,
+                                             Error **errp);
+
+/**
  * memory_region_init_resizeable_ram:  Initialize memory region with resizeable
  *                                     RAM.  Accesses into the region will
  *                                     modify memory directly.  Only an initial
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 7633ef6342..cf2446a176 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -80,7 +80,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
                                  Error **errp);
 RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
                                   MemoryRegion *mr, Error **errp);
-RAMBlock *qemu_ram_alloc(ram_addr_t size, MemoryRegion *mr, Error **errp);
+RAMBlock *qemu_ram_alloc(ram_addr_t size, bool share, MemoryRegion *mr,
+                         Error **errp);
 RAMBlock *qemu_ram_alloc_resizeable(ram_addr_t size, ram_addr_t max_size,
                                     void (*resized)(const char*,
                                                     uint64_t length,
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index adb3758275..41658060a7 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -255,7 +255,7 @@ extern int daemon(int, int);
 int qemu_daemon(int nochdir, int noclose);
 void *qemu_try_memalign(size_t alignment, size_t size);
 void *qemu_memalign(size_t alignment, size_t size);
-void *qemu_anon_ram_alloc(size_t size, uint64_t *align);
+void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared);
 void qemu_vfree(void *ptr);
 void qemu_anon_ram_free(void *ptr, size_t size);
 
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 621a3f9d42..d5ab0b99c6 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -54,7 +54,7 @@ struct HostMemoryBackend {
     char *id;
     uint64_t size;
     bool merge, dump;
-    bool prealloc, force_prealloc, is_mapped;
+    bool prealloc, force_prealloc, is_mapped, share;
     DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
     HostMemPolicy policy;
 
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index bbf12a1723..85002ac49a 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -248,7 +248,7 @@ int kvm_on_sigbus(int code, void *addr);
 
 /* interface with exec.c */
 
-void phys_mem_set_alloc(void *(*alloc)(size_t, uint64_t *align));
+void phys_mem_set_alloc(void *(*alloc)(size_t, uint64_t *align, bool shared));
 
 /* internal API */