[Qemu-devel] [RFC PATCH 4/6] Remove uses of ram.last_offset (aka last_ram_offset)

[Alex Williamson <alex.williamson@redhat.com>]

We currently need this either to allocate the next ram_addr_t for a
new block, or for total memory to be migrated.  Both of which we can
calculate without need of this to keep us in a contiguous address space.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 arch_init.c |   23 ++++++++++++++++-------
 cpu-all.h   |    1 -
 exec.c      |   19 ++++++++++++++-----
 3 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 43e42ba..6103461 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -108,9 +108,10 @@ static int ram_save_block(QEMUFile *f)
     static ram_addr_t current_addr = 0;
     ram_addr_t saved_addr = current_addr;
     ram_addr_t addr = 0;
+    uint64_t total_ram = ram_bytes_total();
     int bytes_sent = 0;
 
-    while (addr < ram.last_offset) {
+    while (addr < total_ram) {
         if (cpu_physical_memory_get_dirty(current_addr, MIGRATION_DIRTY_FLAG)) {
             uint8_t *p;
 
@@ -133,7 +134,7 @@ static int ram_save_block(QEMUFile *f)
             break;
         }
         addr += TARGET_PAGE_SIZE;
-        current_addr = (saved_addr + addr) % ram.last_offset;
+        current_addr = (saved_addr + addr) % total_ram;
     }
 
     return bytes_sent;
@@ -145,8 +146,9 @@ static ram_addr_t ram_save_remaining(void)
 {
     ram_addr_t addr;
     ram_addr_t count = 0;
+    uint64_t total_ram = ram_bytes_total();
 
-    for (addr = 0; addr < ram.last_offset; addr += TARGET_PAGE_SIZE) {
+    for (addr = 0; addr < total_ram; addr += TARGET_PAGE_SIZE) {
         if (cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
             count++;
         }
@@ -167,7 +169,13 @@ uint64_t ram_bytes_transferred(void)
 
 uint64_t ram_bytes_total(void)
 {
-    return ram.last_offset;
+    RAMBlock *block;
+    uint64_t total = 0;
+
+    QLIST_FOREACH(block, &ram.blocks, next)
+        total += block->length;
+
+    return total;
 }
 
 int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
@@ -188,10 +196,11 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
     }
 
     if (stage == 1) {
+        uint64_t total_ram = ram_bytes_total();
         bytes_transferred = 0;
 
         /* Make sure all dirty bits are set */
-        for (addr = 0; addr < ram.last_offset; addr += TARGET_PAGE_SIZE) {
+        for (addr = 0; addr < total_ram; addr += TARGET_PAGE_SIZE) {
             if (!cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
                 cpu_physical_memory_set_dirty(addr);
             }
@@ -200,7 +209,7 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
         /* Enable dirty memory tracking */
         cpu_physical_memory_set_dirty_tracking(1);
 
-        qemu_put_be64(f, ram.last_offset | RAM_SAVE_FLAG_MEM_SIZE);
+        qemu_put_be64(f, total_ram | RAM_SAVE_FLAG_MEM_SIZE);
     }
 
     bytes_transferred_last = bytes_transferred;
@@ -259,7 +268,7 @@ int ram_load(QEMUFile *f, void *opaque, int version_id)
         addr &= TARGET_PAGE_MASK;
 
         if (flags & RAM_SAVE_FLAG_MEM_SIZE) {
-            if (addr != ram.last_offset) {
+            if (addr != ram_bytes_total()) {
                 return -EINVAL;
             }
         }
diff --git a/cpu-all.h b/cpu-all.h
index a5b886a..23b1d1d 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -871,7 +871,6 @@ typedef struct RAMBlock {
 
 typedef struct RAMList {
     uint8_t *phys_dirty;
-    ram_addr_t last_offset;
     QLIST_HEAD(ram, RAMBlock) blocks;
 } RAMList;
 extern RAMList ram;
diff --git a/exec.c b/exec.c
index dd57515..13c0ca0 100644
--- a/exec.c
+++ b/exec.c
@@ -2774,6 +2774,17 @@ static void *file_ram_alloc(ram_addr_t memory, const char *path)
 }
 #endif
 
+static ram_addr_t find_ram_offset(ram_addr_t size)
+{
+    RAMBlock *block;
+    ram_addr_t last = 0;
+
+    QLIST_FOREACH(block, &ram.blocks, next)
+        last = MAX(last, block->offset + block->length);
+
+    return last;
+}
+
 ram_addr_t qemu_ram_map(const char *name, ram_addr_t size, void *host)
 {
     RAMBlock *new_block;
@@ -2785,18 +2796,16 @@ ram_addr_t qemu_ram_map(const char *name, ram_addr_t size, void *host)
     snprintf(new_block->name, sizeof(new_block->name), "%s", strdup(name));
     new_block->host = host;
 
-    new_block->offset = ram.last_offset;
+    new_block->offset = find_ram_offset(size);
     new_block->length = size;
 
     QLIST_INSERT_HEAD(&ram.blocks, new_block, next);
 
     ram.phys_dirty = qemu_realloc(ram.phys_dirty,
-        (ram.last_offset + size) >> TARGET_PAGE_BITS);
-    memset(ram.phys_dirty + (ram.last_offset >> TARGET_PAGE_BITS),
+        (new_block->offset + size) >> TARGET_PAGE_BITS);
+    memset(ram.phys_dirty + (new_block->offset >> TARGET_PAGE_BITS),
            0xff, size >> TARGET_PAGE_BITS);
 
-    ram.last_offset += size;
-
     if (kvm_enabled())
         kvm_setup_guest_memory(new_block->host, size);