Add qemu_ram_remap

qemu_ram_remap() unmaps the specified RAM pages, then re-maps these
pages again.  This is used by KVM HWPoison support to clear HWPoisoned
page tables across guest rebooting, so that a new page may be
allocated later to recover the memory error.

[ Jan: style fixlets, WIN32 fix ]

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

cpu-all.h

@@ -863,10 +863,14 @@ target_phys_addr_t cpu_get_phys_page_debug(CPUState *env, target_ulong addr);
 extern int phys_ram_fd;
 extern ram_addr_t ram_size;
 
+/* RAM is pre-allocated and passed into qemu_ram_alloc_from_ptr */
+#define RAM_PREALLOC_MASK   (1 << 0)
+
 typedef struct RAMBlock {
     uint8_t *host;
     ram_addr_t offset;
     ram_addr_t length;
+    uint32_t flags;
     char idstr[256];
     QLIST_ENTRY(RAMBlock) next;
 #if defined(__linux__) && !defined(TARGET_S390X)

cpu-common.h

@@ -50,6 +50,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState *dev, const char *name,
                         ram_addr_t size, void *host);
 ram_addr_t qemu_ram_alloc(DeviceState *dev, const char *name, ram_addr_t size);
 void qemu_ram_free(ram_addr_t addr);
+void qemu_ram_remap(ram_addr_t addr, ram_addr_t length);
 /* This should only be used for ram local to a device.  */
 void *qemu_get_ram_ptr(ram_addr_t addr);
 /* Same but slower, to use for migration, where the order of

exec.c

@@ -2867,6 +2867,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(DeviceState *dev, const char *name,
 
     if (host) {
         new_block->host = host;
+        new_block->flags |= RAM_PREALLOC_MASK;
     } else {
         if (mem_path) {
 #if defined (__linux__) && !defined(TARGET_S390X)
@@ -2920,7 +2921,9 @@ void qemu_ram_free(ram_addr_t addr)
     QLIST_FOREACH(block, &ram_list.blocks, next) {
         if (addr == block->offset) {
             QLIST_REMOVE(block, next);
-            if (mem_path) {
+            if (block->flags & RAM_PREALLOC_MASK) {
+                ;
+            } else if (mem_path) {
 #if defined (__linux__) && !defined(TARGET_S390X)
                 if (block->fd) {
                     munmap(block->host, block->length);
@@ -2943,6 +2946,64 @@ void qemu_ram_free(ram_addr_t addr)
 
 }
 
+#ifndef _WIN32
+void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
+{
+    RAMBlock *block;
+    ram_addr_t offset;
+    int flags;
+    void *area, *vaddr;
+
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        offset = addr - block->offset;
+        if (offset < block->length) {
+            vaddr = block->host + offset;
+            if (block->flags & RAM_PREALLOC_MASK) {
+                ;
+            } else {
+                flags = MAP_FIXED;
+                munmap(vaddr, length);
+                if (mem_path) {
+#if defined(__linux__) && !defined(TARGET_S390X)
+                    if (block->fd) {
+#ifdef MAP_POPULATE
+                        flags |= mem_prealloc ? MAP_POPULATE | MAP_SHARED :
+                            MAP_PRIVATE;
+#else
+                        flags |= MAP_PRIVATE;
+#endif
+                        area = mmap(vaddr, length, PROT_READ | PROT_WRITE,
+                                    flags, block->fd, offset);
+                    } else {
+                        flags |= MAP_PRIVATE | MAP_ANONYMOUS;
+                        area = mmap(vaddr, length, PROT_READ | PROT_WRITE,
+                                    flags, -1, 0);
+                    }
+#endif
+                } else {
+#if defined(TARGET_S390X) && defined(CONFIG_KVM)
+                    flags |= MAP_SHARED | MAP_ANONYMOUS;
+                    area = mmap(vaddr, length, PROT_EXEC|PROT_READ|PROT_WRITE,
+                                flags, -1, 0);
+#else
+                    flags |= MAP_PRIVATE | MAP_ANONYMOUS;
+                    area = mmap(vaddr, length, PROT_READ | PROT_WRITE,
+                                flags, -1, 0);
+#endif
+                }
+                if (area != vaddr) {
+                    fprintf(stderr, "Could not remap addr: %lx@%lx\n",
+                            length, addr);
+                    exit(1);
+                }
+                qemu_madvise(vaddr, length, QEMU_MADV_MERGEABLE);
+            }
+            return;
+        }
+    }
+}
+#endif /* !_WIN32 */
+
 /* Return a host pointer to ram allocated with qemu_ram_alloc.
    With the exception of the softmmu code in this file, this should
    only be used for local memory (e.g. video ram) that the device owns,