[Xen-devel] [PATCH] xen: use same main loop for counting and remapping pages

[Juergen Gross <jgross@xxxxxxxx>]

Instead of having two functions for cycling through the E820 map in
order to count to be remapped pages and remap them later, just use one
function with a caller supplied sub-function called for each region to
be processed. This eliminates the possibility of a mismatch between
both loops which showed up in certain configurations.

Suggested-by: Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 arch/x86/xen/setup.c | 65 +++++++++++++++++++++-------------------------------
 1 file changed, 26 insertions(+), 39 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 7ab2951..e345891 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -393,6 +393,9 @@ static unsigned long __init 
xen_set_identity_and_remap_chunk(
        unsigned long i = 0;
        unsigned long n = end_pfn - start_pfn;
 
+       if (remap_pfn == 0)
+               remap_pfn = nr_pages;
+
        while (i < n) {
                unsigned long cur_pfn = start_pfn + i;
                unsigned long left = n - i;
@@ -438,17 +441,29 @@ static unsigned long __init 
xen_set_identity_and_remap_chunk(
        return remap_pfn;
 }
 
-static void __init xen_set_identity_and_remap(unsigned long nr_pages)
+static unsigned long __init xen_count_remap_pages(
+       unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages,
+       unsigned long remap_pages)
+{
+       if (start_pfn >= nr_pages)
+               return remap_pages;
+
+       return remap_pages + min(end_pfn, nr_pages) - start_pfn;
+}
+
+static unsigned long __init xen_foreach_remap_area(unsigned long nr_pages,
+       unsigned long (*func)(unsigned long start_pfn, unsigned long end_pfn,
+                             unsigned long nr_pages, unsigned long last_val))
 {
        phys_addr_t start = 0;
-       unsigned long last_pfn = nr_pages;
+       unsigned long ret_val = 0;
        const struct e820entry *entry = xen_e820_map;
        int i;
 
        /*
         * Combine non-RAM regions and gaps until a RAM region (or the
-        * end of the map) is reached, then set the 1:1 map and
-        * remap the memory in those non-RAM regions.
+        * end of the map) is reached, then call the provided function
+        * to perform its duty on the non-RAM region.
         *
         * The combined non-RAM regions are rounded to a whole number
         * of pages so any partial pages are accessible via the 1:1
@@ -466,14 +481,13 @@ static void __init xen_set_identity_and_remap(unsigned 
long nr_pages)
                                end_pfn = PFN_UP(entry->addr);
 
                        if (start_pfn < end_pfn)
-                               last_pfn = xen_set_identity_and_remap_chunk(
-                                               start_pfn, end_pfn, nr_pages,
-                                               last_pfn);
+                               ret_val = func(start_pfn, end_pfn, nr_pages,
+                                              ret_val);
                        start = end;
                }
        }
 
-       pr_info("Released %ld page(s)\n", xen_released_pages);
+       return ret_val;
 }
 
 /*
@@ -596,35 +610,6 @@ static void __init xen_ignore_unusable(void)
        }
 }
 
-static unsigned long __init xen_count_remap_pages(unsigned long max_pfn)
-{
-       unsigned long extra = 0;
-       unsigned long start_pfn, end_pfn;
-       const struct e820entry *entry = xen_e820_map;
-       int i;
-
-       end_pfn = 0;
-       for (i = 0; i < xen_e820_map_entries; i++, entry++) {
-               start_pfn = PFN_DOWN(entry->addr);
-               /* Adjacent regions on non-page boundaries handling! */
-               end_pfn = min(end_pfn, start_pfn);
-
-               if (start_pfn >= max_pfn)
-                       return extra + max_pfn - end_pfn;
-
-               /* Add any holes in map to result. */
-               extra += start_pfn - end_pfn;
-
-               end_pfn = PFN_UP(entry->addr + entry->size);
-               end_pfn = min(end_pfn, max_pfn);
-
-               if (entry->type != E820_RAM)
-                       extra += end_pfn - start_pfn;
-       }
-
-       return extra;
-}
-
 bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size)
 {
        struct e820entry *entry;
@@ -804,7 +789,7 @@ char * __init xen_memory_setup(void)
        max_pages = xen_get_max_pages();
 
        /* How many extra pages do we need due to remapping? */
-       max_pages += xen_count_remap_pages(max_pfn);
+       max_pages += xen_foreach_remap_area(max_pfn, xen_count_remap_pages);
 
        if (max_pages > max_pfn)
                extra_pages += max_pages - max_pfn;
@@ -922,7 +907,9 @@ char * __init xen_memory_setup(void)
         * Set identity map on non-RAM pages and prepare remapping the
         * underlying RAM.
         */
-       xen_set_identity_and_remap(max_pfn);
+       xen_foreach_remap_area(max_pfn, xen_set_identity_and_remap_chunk);
+
+       pr_info("Released %ld page(s)\n", xen_released_pages);
 
        return "Xen";
 }
-- 
2.6.6


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