[Qemu-devel] TARGET_PAGE_SIZE > host page size

["Edgar E. Iglesias" <edgar.iglesias@axis.com>]

Hello,

I'm working on a new target port and the linux-user emulation is fairly functional and passing quite extensive test-suites.

I've got a problem though, my target has 8K page sizes, so for example when running on a x86 host TARGET_PAGE_SIZE > host page size.

I'm not very familiar with linux-user/mmap.c, but I though I'd let you know that with this patch things seem to be working fine for me. I am not sure if the patch is correct so if anyone with more experience sees an obvious flaw I'd appreciate to know.

Thanks!
Edgar E. Iglesias
Axis Communications AB

Index: linux-user/mmap.c
===================================================================
RCS file: /sources/qemu/qemu/linux-user/mmap.c,v
retrieving revision 1.14
diff -u -p -b -u -p -r1.14 mmap.c
--- linux-user/mmap.c	17 Sep 2007 08:09:49 -0000	1.14
+++ linux-user/mmap.c	21 Sep 2007 13:24:42 -0000
@@ -209,26 +209,34 @@ long target_mmap(target_ulong start, tar
             last_start += HOST_PAGE_ALIGN(len);
         }
 #endif
-        if (0 && qemu_host_page_size != qemu_real_host_page_size) {
+        if (qemu_host_page_size != qemu_real_host_page_size) {
             /* NOTE: this code is only for debugging with '-p' option */
             /* ??? Can also occur when TARGET_PAGE_SIZE > host page size.  */
             /* reserve a memory area */
             /* ??? This needs fixing for remapping.  */
-abort();
-            host_len = HOST_PAGE_ALIGN(len) + qemu_host_page_size - TARGET_PAGE_SIZE;
+
+	    /* Make sure we have enough room for fixing up the buffer.  */
+	    host_len = HOST_PAGE_ALIGN(len + TARGET_PAGE_SIZE);
             real_start = (long)mmap(g2h(real_start), host_len, PROT_NONE,
                                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
             if (real_start == -1)
                 return real_start;
             real_end = real_start + host_len;
-            start = HOST_PAGE_ALIGN(real_start);
-            end = start + HOST_PAGE_ALIGN(len);
+
+	    /* Find start and end, aligned to the targets pagesize with-in the
+	       mmaped area.  */
+            start = TARGET_PAGE_ALIGN(real_start);
+            end = start + TARGET_PAGE_ALIGN(len);
+	    /* Chop off the leftovers, if any.  */
             if (start > real_start)
                 munmap((void *)real_start, start - real_start);
             if (end < real_end)
                 munmap((void *)end, real_end - end);
             /* use it as a fixed mapping */
             flags |= MAP_FIXED;
+	    /* These are now real.  */
+	    real_start = start;
+	    real_end = end;
         } else {
             /* if not fixed, no need to do anything */
             host_offset = offset & qemu_host_page_mask;