Re: [Qemu-devel] Re: [Qemu-commits] [COMMIT 3086844] Instead of writing a zero page, madvise it away

[Anthony Liguori <aliguori@us.ibm.com>]

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See attached.

-- 
Regards,

Anthony Liguori


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commit a70787dc8200dad03f3d3a85fdb40497f336f12b
Author: Anthony Liguori <aliguori@us.ibm.com>
Date:   Mon Jun 22 12:39:00 2009 -0500

    Make sure to zero out memory before calling madvise to increase robustness
    
    Avi pointed out that it's not entirely safe to rely on madvise zeroing out
    memory.  So let's do it explicitly before calling madvise.
    
    Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/vl.c b/vl.c
index 60a00e1..1c077b4 100644
--- a/vl.c
+++ b/vl.c
@@ -3358,13 +3358,13 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
         
         if (flags & RAM_SAVE_FLAG_COMPRESS) {
             uint8_t ch = qemu_get_byte(f);
-#if defined(__linux__)
+            memset(qemu_get_ram_ptr(addr), ch, TARGET_PAGE_SIZE);
+#ifndef _WIN32
             if (ch == 0 &&
                 (!kvm_enabled() || kvm_has_sync_mmu())) {
                 madvise(qemu_get_ram_ptr(addr), TARGET_PAGE_SIZE, MADV_DONTNEED);
-            } else
+            }
 #endif
-            memset(qemu_get_ram_ptr(addr), ch, TARGET_PAGE_SIZE);
         } else if (flags & RAM_SAVE_FLAG_PAGE)
             qemu_get_buffer(f, qemu_get_ram_ptr(addr), TARGET_PAGE_SIZE);
     } while (!(flags & RAM_SAVE_FLAG_EOS));