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* [Qemu-devel] [PATCH] Revert "memory: syncronize kvm bitmap using bitmaps operations"
@ 2014-01-29  5:50 Alexey Kardashevskiy
  2014-01-29  7:30 ` Paolo Bonzini
  0 siblings, 1 reply; 6+ messages in thread
From: Alexey Kardashevskiy @ 2014-01-29  5:50 UTC (permalink / raw)
  To: qemu-devel
  Cc: Alexey Kardashevskiy, Orit Wasserman, Paolo Bonzini,
	Juan Quintela

This reverts commit ae2810c4bb3b383176e8e1b33931b16c01483aab.

This reverts the optimization introduced by the original patch as
it breaks dirty page tracking on systems where
getpagesize() != TARGET_PAGE_SIZE such as POWERPC64.

The cpu_physical_memory_set_dirty_lebitmap() is called from
the kvm_physical_sync_dirty_bitmap() with the bitmap returned by
the KVM's KVM_GET_DIRTY_LOG ioctl where 1 bit is per the system
page. However QEMU's ram_list.dirty_memory maps are allocated to store
1 bit per TARGET_PAGE_SIZE which is hardcoded to 4K.

Since 64K system page size is quite popular configuration on PPC64,
the original patch breaks migration.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 include/exec/ram_addr.h | 54 +++++++++++++++++--------------------------------
 1 file changed, 18 insertions(+), 36 deletions(-)

diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 33c8acc..c6736ed 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -83,47 +83,29 @@ static inline void cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap,
                                                           ram_addr_t start,
                                                           ram_addr_t pages)
 {
-    unsigned long i, j;
+    unsigned int i, j;
     unsigned long page_number, c;
     hwaddr addr;
     ram_addr_t ram_addr;
-    unsigned long len = (pages + HOST_LONG_BITS - 1) / HOST_LONG_BITS;
+    unsigned int len = (pages + HOST_LONG_BITS - 1) / HOST_LONG_BITS;
     unsigned long hpratio = getpagesize() / TARGET_PAGE_SIZE;
-    unsigned long page = BIT_WORD(start >> TARGET_PAGE_BITS);
 
-    /* start address is aligned at the start of a word? */
-    if (((page * BITS_PER_LONG) << TARGET_PAGE_BITS) == start) {
-        long k;
-        long nr = BITS_TO_LONGS(pages);
-
-        for (k = 0; k < nr; k++) {
-            if (bitmap[k]) {
-                unsigned long temp = leul_to_cpu(bitmap[k]);
-
-                ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION][page + k] |= temp;
-                ram_list.dirty_memory[DIRTY_MEMORY_VGA][page + k] |= temp;
-                ram_list.dirty_memory[DIRTY_MEMORY_CODE][page + k] |= temp;
-            }
-        }
-        xen_modified_memory(start, pages);
-    } else {
-        /*
-         * bitmap-traveling is faster than memory-traveling (for addr...)
-         * especially when most of the memory is not dirty.
-         */
-        for (i = 0; i < len; i++) {
-            if (bitmap[i] != 0) {
-                c = leul_to_cpu(bitmap[i]);
-                do {
-                    j = ffsl(c) - 1;
-                    c &= ~(1ul << j);
-                    page_number = (i * HOST_LONG_BITS + j) * hpratio;
-                    addr = page_number * TARGET_PAGE_SIZE;
-                    ram_addr = start + addr;
-                    cpu_physical_memory_set_dirty_range(ram_addr,
-                                       TARGET_PAGE_SIZE * hpratio);
-                } while (c != 0);
-            }
+    /*
+     * bitmap-traveling is faster than memory-traveling (for addr...)
+     * especially when most of the memory is not dirty.
+     */
+    for (i = 0; i < len; i++) {
+        if (bitmap[i] != 0) {
+            c = leul_to_cpu(bitmap[i]);
+            do {
+                j = ffsl(c) - 1;
+                c &= ~(1ul << j);
+                page_number = (i * HOST_LONG_BITS + j) * hpratio;
+                addr = page_number * TARGET_PAGE_SIZE;
+                ram_addr = start + addr;
+                cpu_physical_memory_set_dirty_range(ram_addr,
+                                                    TARGET_PAGE_SIZE * hpratio);
+            } while (c != 0);
         }
     }
 }
-- 
1.8.4.rc4

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2014-01-30 12:07 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-01-29  5:50 [Qemu-devel] [PATCH] Revert "memory: syncronize kvm bitmap using bitmaps operations" Alexey Kardashevskiy
2014-01-29  7:30 ` Paolo Bonzini
2014-01-29  8:12   ` Alexey Kardashevskiy
2014-01-29 10:03     ` Paolo Bonzini
2014-01-30 12:07       ` Alexey Kardashevskiy
2014-01-29 10:39     ` Juan Quintela

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