Re: [Qemu-devel] Regression bug

["Blue Swirl" <blauwirbel@gmail.com>]

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On 5/29/07, risc@volumehost.com <risc@volumehost.com> wrote:
> On Tue, May 29, 2007 at 09:44:39PM +0300, Blue Swirl wrote:
> > Hi,
> >
> > I found a bug in the subpage checking code. Could you try if the
> > attached patch fixes the problem?
>
> thats a negative. the exact same behavior as before.

Thanks.

The bug was actually that on PC, the very last addresses are mapped,
and the current code failed when the start_addr + size wrapped back to
0. That didn't happen on amd64, where I first tried to reproduce the
bug.

The attached patch fixes the problem for me, I'll commit it if there
are no objections.

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Index: qemu/exec.c
===================================================================
--- qemu.orig/exec.c	2007-05-29 19:31:15.000000000 +0000
+++ qemu/exec.c	2007-05-29 19:31:24.000000000 +0000
@@ -1922,7 +1922,7 @@
                 need_subpage = 1;                                       \
         }                                                               \
                                                                         \
-        if (end_addr - addr > TARGET_PAGE_SIZE)                         \
+        if ((start_addr + orig_size) - addr >= TARGET_PAGE_SIZE)        \
             end_addr2 = TARGET_PAGE_SIZE - 1;                           \
         else {                                                          \
             end_addr2 = (start_addr + orig_size - 1) & ~TARGET_PAGE_MASK; \
@@ -1944,9 +1944,9 @@
     unsigned long orig_size = size;
     void *subpage;
 
-    end_addr = start_addr + (target_phys_addr_t)size;
     size = (size + TARGET_PAGE_SIZE - 1) & TARGET_PAGE_MASK;
-    for(addr = start_addr; addr < end_addr; addr += TARGET_PAGE_SIZE) {
+    end_addr = start_addr + (target_phys_addr_t)size;
+    for(addr = start_addr; addr != end_addr; addr += TARGET_PAGE_SIZE) {
         p = phys_page_find(addr >> TARGET_PAGE_BITS);
         if (p && p->phys_offset != IO_MEM_UNASSIGNED) {
             unsigned long orig_memory = p->phys_offset;