[RFC v4 PATCH 01/49] multi-process: memory: alloc RAM from file at offset

[Jagannathan Raman <jag.raman@oracle.com>]

Allow RAM MemoryRegion to be created from an offset in a file, instead
of allocating at offset of 0 by default. This is needed to synchronize
RAM between QEMU & remote process.
This will be needed for the following patches.

Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
---
 exec.c                    | 11 +++++++----
 include/exec/ram_addr.h   |  2 +-
 include/qemu/mmap-alloc.h |  3 ++-
 memory.c                  |  2 +-
 util/mmap-alloc.c         |  7 ++++---
 util/oslib-posix.c        |  2 +-
 6 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/exec.c b/exec.c
index fb0943c..08c4181 100644
--- a/exec.c
+++ b/exec.c
@@ -1871,6 +1871,7 @@ static void *file_ram_alloc(RAMBlock *block,
                             ram_addr_t memory,
                             int fd,
                             bool truncate,
+                            off_t offset,
                             Error **errp)
 {
     MachineState *ms = MACHINE(qdev_get_machine());
@@ -1922,7 +1923,8 @@ static void *file_ram_alloc(RAMBlock *block,
     }
 
     area = qemu_ram_mmap(fd, memory, block->mr->align,
-                         block->flags & RAM_SHARED, block->flags & RAM_PMEM);
+                         block->flags & RAM_SHARED, block->flags & RAM_PMEM,
+                         offset);
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
                          "unable to map backing store for guest RAM");
@@ -2309,7 +2311,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp, bool shared)
 #ifdef CONFIG_POSIX
 RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
                                  uint32_t ram_flags, int fd,
-                                 Error **errp)
+                                 off_t offset, Error **errp)
 {
     RAMBlock *new_block;
     Error *local_err = NULL;
@@ -2354,7 +2356,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
     new_block->used_length = size;
     new_block->max_length = size;
     new_block->flags = ram_flags;
-    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, errp);
+    new_block->host = file_ram_alloc(new_block, size, fd, !file_size, offset,
+                                     errp);
     if (!new_block->host) {
         g_free(new_block);
         return NULL;
@@ -2384,7 +2387,7 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
         return NULL;
     }
 
-    block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, errp);
+    block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, 0, errp);
     if (!block) {
         if (created) {
             unlink(mem_path);
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index ad158bb..92134c0 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -159,7 +159,7 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
                                    Error **errp);
 RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
                                  uint32_t ram_flags, int fd,
-                                 Error **errp);
+                                 off_t offset, Error **errp);
 
 RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
                                   MemoryRegion *mr, Error **errp);
diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
index e786266..4f57985 100644
--- a/include/qemu/mmap-alloc.h
+++ b/include/qemu/mmap-alloc.h
@@ -25,7 +25,8 @@ void *qemu_ram_mmap(int fd,
                     size_t size,
                     size_t align,
                     bool shared,
-                    bool is_pmem);
+                    bool is_pmem,
+                    off_t start);
 
 void qemu_ram_munmap(int fd, void *ptr, size_t size);
 
diff --git a/memory.c b/memory.c
index c952eab..c25c74f 100644
--- a/memory.c
+++ b/memory.c
@@ -1602,7 +1602,7 @@ void memory_region_init_ram_from_fd(MemoryRegion *mr,
     mr->destructor = memory_region_destructor_ram;
     mr->ram_block = qemu_ram_alloc_from_fd(size, mr,
                                            share ? RAM_SHARED : 0,
-                                           fd, &err);
+                                           fd, 0, &err);
     mr->dirty_log_mask = tcg_enabled() ? (1 << DIRTY_MEMORY_CODE) : 0;
     if (err) {
         mr->size = int128_zero();
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index f7f177d..4b727bd 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -86,7 +86,8 @@ void *qemu_ram_mmap(int fd,
                     size_t size,
                     size_t align,
                     bool shared,
-                    bool is_pmem)
+                    bool is_pmem,
+                    off_t start)
 {
     int flags;
     int map_sync_flags = 0;
@@ -147,7 +148,7 @@ void *qemu_ram_mmap(int fd,
     offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;
 
     ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
-               flags | map_sync_flags, fd, 0);
+               flags | map_sync_flags, fd, start);
 
     if (ptr == MAP_FAILED && map_sync_flags) {
         if (errno == ENOTSUP) {
@@ -172,7 +173,7 @@ void *qemu_ram_mmap(int fd,
          * we will remove these flags to handle compatibility.
          */
         ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE,
-                   flags, fd, 0);
+                   flags, fd, start);
     }
 
     if (ptr == MAP_FAILED) {
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index f869338..bdfcdcf 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -205,7 +205,7 @@ void *qemu_memalign(size_t alignment, size_t size)
 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared)
 {
     size_t align = QEMU_VMALLOC_ALIGN;
-    void *ptr = qemu_ram_mmap(-1, size, align, shared, false);
+    void *ptr = qemu_ram_mmap(-1, size, align, shared, false, 0);
 
     if (ptr == MAP_FAILED) {
         return NULL;
-- 
1.8.3.1