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>

1 files changed, 15 insertions, 11 deletions

diff --git a/exec.c b/exec.c
index e8d7b33..4d8addb 100644
--- a/exec.c
+++ b/exec.c
@@ -1285,7 +1285,7 @@ static int subpage_register (subpage_t *mmio, uint32_t start, uint32_t end,
                              uint16_t section);
 static subpage_t *subpage_init(FlatView *fv, hwaddr base);
 
-static void *(*phys_mem_alloc)(size_t size, uint64_t *align) =
+static void *(*phys_mem_alloc)(size_t size, uint64_t *align, bool shared) =
                                qemu_anon_ram_alloc;
 
 /*
@@ -1293,7 +1293,7 @@ static void *(*phys_mem_alloc)(size_t size, uint64_t *align) =
  * Accelerators with unusual needs may need this.  Hopefully, we can
  * get rid of it eventually.
  */
-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))
 {
     phys_mem_alloc = alloc;
 }
@@ -1921,7 +1921,7 @@ static void dirty_memory_extend(ram_addr_t old_ram_size,
     }
 }
 
-static void ram_block_add(RAMBlock *new_block, Error **errp)
+static void ram_block_add(RAMBlock *new_block, Error **errp, bool shared)
 {
     RAMBlock *block;
     RAMBlock *last_block = NULL;
@@ -1944,7 +1944,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
             }
         } else {
             new_block->host = phys_mem_alloc(new_block->max_length,
-                                             &new_block->mr->align);
+                                             &new_block->mr->align, shared);
             if (!new_block->host) {
                 error_setg_errno(errp, errno,
                                  "cannot set up guest memory '%s'",
@@ -2049,7 +2049,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
         return NULL;
     }
 
-    ram_block_add(new_block, &local_err);
+    ram_block_add(new_block, &local_err, share);
     if (local_err) {
         g_free(new_block);
         error_propagate(errp, local_err);
@@ -2091,7 +2091,7 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
                                   void (*resized)(const char*,
                                                   uint64_t length,
                                                   void *host),
-                                  void *host, bool resizeable,
+                                  void *host, bool resizeable, bool share,
                                   MemoryRegion *mr, Error **errp)
 {
     RAMBlock *new_block;
@@ -2114,7 +2114,7 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
     if (resizeable) {
         new_block->flags |= RAM_RESIZEABLE;
     }
-    ram_block_add(new_block, &local_err);
+    ram_block_add(new_block, &local_err, share);
     if (local_err) {
         g_free(new_block);
         error_propagate(errp, local_err);
@@ -2126,12 +2126,15 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
 RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
                                    MemoryRegion *mr, Error **errp)
 {
-    return qemu_ram_alloc_internal(size, size, NULL, host, false, mr, errp);
+    return qemu_ram_alloc_internal(size, size, NULL, host, false,
+                                   false, mr, 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)
 {
-    return qemu_ram_alloc_internal(size, size, NULL, NULL, false, mr, errp);
+    return qemu_ram_alloc_internal(size, size, NULL, NULL, false,
+                                   share, mr, errp);
 }
 
 RAMBlock *qemu_ram_alloc_resizeable(ram_addr_t size, ram_addr_t maxsz,
@@ -2140,7 +2143,8 @@ RAMBlock *qemu_ram_alloc_resizeable(ram_addr_t size, ram_addr_t maxsz,
                                                      void *host),
                                      MemoryRegion *mr, Error **errp)
 {
-    return qemu_ram_alloc_internal(size, maxsz, resized, NULL, true, mr, errp);
+    return qemu_ram_alloc_internal(size, maxsz, resized, NULL, true,
+                                   false, mr, errp);
 }
 
 static void reclaim_ramblock(RAMBlock *block)