memory: expose alignment used for allocating RAM as MemoryRegion API

introduce memory_region_get_alignment() that returns
underlying memory block alignment or 0 if it's not
relevant/implemented for backend.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

exec.c

@@ -909,14 +909,15 @@ static int subpage_register (subpage_t *mmio, uint32_t start, uint32_t end,
                              uint16_t section);
 static subpage_t *subpage_init(AddressSpace *as, hwaddr base);
 
-static void *(*phys_mem_alloc)(size_t size) = qemu_anon_ram_alloc;
+static void *(*phys_mem_alloc)(size_t size, uint64_t *align) =
+                               qemu_anon_ram_alloc;
 
 /*
  * Set a custom physical guest memory alloator.
  * Accelerators with unusual needs may need this.  Hopefully, we can
  * get rid of it eventually.
  */
-void phys_mem_set_alloc(void *(*alloc)(size_t))
+void phys_mem_set_alloc(void *(*alloc)(size_t, uint64_t *align))
 {
     phys_mem_alloc = alloc;
 }
@@ -1098,6 +1099,7 @@ static void *file_ram_alloc(RAMBlock *block,
         error_propagate(errp, local_err);
         goto error;
     }
+    block->mr->align = hpagesize;
 
     if (memory < hpagesize) {
         error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
@@ -1309,7 +1311,8 @@ static ram_addr_t ram_block_add(RAMBlock *new_block, Error **errp)
         if (xen_enabled()) {
             xen_ram_alloc(new_block->offset, new_block->length, new_block->mr);
         } else {
-            new_block->host = phys_mem_alloc(new_block->length);
+            new_block->host = phys_mem_alloc(new_block->length,
+                                             &new_block->mr->align);
             if (!new_block->host) {
                 error_setg_errno(errp, errno,
                                  "cannot set up guest memory '%s'",

include/exec/exec-all.h

@@ -333,7 +333,7 @@ extern uintptr_t tci_tb_ptr;
 
 #if !defined(CONFIG_USER_ONLY)
 
-void phys_mem_set_alloc(void *(*alloc)(size_t));
+void phys_mem_set_alloc(void *(*alloc)(size_t, uint64_t *align));
 
 struct MemoryRegion *iotlb_to_region(AddressSpace *as, hwaddr index);
 bool io_mem_read(struct MemoryRegion *mr, hwaddr addr,

include/exec/memory.h

@@ -146,6 +146,7 @@ struct MemoryRegion {
     hwaddr addr;
     void (*destructor)(MemoryRegion *mr);
     ram_addr_t ram_addr;
+    uint64_t align;
     bool subpage;
     bool terminates;
     bool romd_mode;
@@ -838,6 +839,7 @@ void memory_region_add_subregion_overlap(MemoryRegion *mr,
  */
 ram_addr_t memory_region_get_ram_addr(MemoryRegion *mr);
 
+uint64_t memory_region_get_alignment(const MemoryRegion *mr);
 /**
  * memory_region_del_subregion: Remove a subregion.
  *

include/qemu/osdep.h

@@ -5,6 +5,7 @@
 #include <stdarg.h>
 #include <stddef.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <sys/types.h>
 #ifdef __OpenBSD__
 #include <sys/signal.h>
@@ -103,7 +104,7 @@ typedef signed int              int_fast16_t;
 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);
+void *qemu_anon_ram_alloc(size_t size, uint64_t *align);
 void qemu_vfree(void *ptr);
 void qemu_anon_ram_free(void *ptr, size_t size);
 

memory.c

@@ -1749,6 +1749,11 @@ ram_addr_t memory_region_get_ram_addr(MemoryRegion *mr)
     return mr->ram_addr;
 }
 
+uint64_t memory_region_get_alignment(const MemoryRegion *mr)
+{
+    return mr->align;
+}
+
 static int cmp_flatrange_addr(const void *addr_, const void *fr_)
 {
     const AddrRange *addr = addr_;

target-s390x/kvm.c

@@ -404,7 +404,7 @@ int kvm_arch_get_registers(CPUState *cs)
  * to grow. We also have to use MAP parameters that avoid
  * read-only mapping of guest pages.
  */
-static void *legacy_s390_alloc(size_t size)
+static void *legacy_s390_alloc(size_t size, , uint64_t *align)
 {
     void *mem;
 

util/oslib-posix.c

@@ -124,7 +124,7 @@ void *qemu_memalign(size_t alignment, size_t size)
 }
 
 /* alloc shared memory pages */
-void *qemu_anon_ram_alloc(size_t size)
+void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment)
 {
     size_t align = QEMU_VMALLOC_ALIGN;
     size_t total = size + align - getpagesize();
@@ -136,6 +136,9 @@ void *qemu_anon_ram_alloc(size_t size)
         return NULL;
     }
 
+    if (alignment) {
+        *alignment = align;
+    }
     ptr += offset;
     total -= offset;
 

util/oslib-win32.c

@@ -67,7 +67,7 @@ void *qemu_memalign(size_t alignment, size_t size)
     return qemu_oom_check(qemu_try_memalign(alignment, size));
 }
 
-void *qemu_anon_ram_alloc(size_t size)
+void *qemu_anon_ram_alloc(size_t size, uint64_t *align)
 {
     void *ptr;