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[Xen-devel] [PATCH 3/5] xen: allow balloon driver to use more than one memory region



Allow the xen balloon driver to populate its list of extra pages from
more than one region of memory.  This will allow platforms to provide
(for example) a region of low memory and a region of high memory.

The maximum possible number of extra regions is 128 (== E820MAX) which
is quite large so xen_extra_mem is placed in __initdata.  This is safe
as both xen_memeory_setup() and balloon_init() are in __init.

The balloon regions themselves are not altered (i.e., there is still
only the one region).

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 arch/x86/xen/setup.c  |   20 +++++++++---------
 drivers/xen/balloon.c |   51 ++++++++++++++++++++++++++++--------------------
 include/xen/page.h    |    9 +++++++-
 3 files changed, 48 insertions(+), 32 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c3b8d44..4720c2d 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -37,7 +37,7 @@ extern void xen_syscall_target(void);
 extern void xen_syscall32_target(void);
 
 /* Amount of extra memory space we add to the e820 ranges */
-phys_addr_t xen_extra_mem_start, xen_extra_mem_size;
+struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
 
 /* 
  * The maximum amount of extra memory compared to the base size.  The
@@ -56,7 +56,7 @@ static void __init xen_add_extra_mem(unsigned long pages)
        unsigned long pfn;
 
        u64 size = (u64)pages * PAGE_SIZE;
-       u64 extra_start = xen_extra_mem_start + xen_extra_mem_size;
+       u64 extra_start = xen_extra_mem[0].start + xen_extra_mem[0].size;
 
        if (!pages)
                return;
@@ -66,7 +66,7 @@ static void __init xen_add_extra_mem(unsigned long pages)
 
        memblock_x86_reserve_range(extra_start, extra_start + size, "XEN 
EXTRA");
 
-       xen_extra_mem_size += size;
+       xen_extra_mem[0].size += size;
 
        xen_max_p2m_pfn = PFN_DOWN(extra_start + size);
 
@@ -239,7 +239,7 @@ char * __init xen_memory_setup(void)
 
        memcpy(map_raw, map, sizeof(map));
        e820.nr_map = 0;
-       xen_extra_mem_start = mem_end;
+       xen_extra_mem[0].start = mem_end;
        for (i = 0; i < memmap.nr_entries; i++) {
                unsigned long long end;
 
@@ -267,8 +267,8 @@ char * __init xen_memory_setup(void)
                                e820_add_region(end, delta, E820_UNUSABLE);
                }
 
-               if (map[i].size > 0 && end > xen_extra_mem_start)
-                       xen_extra_mem_start = end;
+               if (map[i].size > 0 && end > xen_extra_mem[0].start)
+                       xen_extra_mem[0].start = end;
 
                /* Add region if any remains */
                if (map[i].size > 0)
@@ -276,10 +276,10 @@ char * __init xen_memory_setup(void)
        }
        /* Align the balloon area so that max_low_pfn does not get set
         * to be at the _end_ of the PCI gap at the far end (fee01000).
-        * Note that xen_extra_mem_start gets set in the loop above to be
-        * past the last E820 region. */
-       if (xen_initial_domain() && (xen_extra_mem_start < (1ULL<<32)))
-               xen_extra_mem_start = (1ULL<<32);
+        * Note that the start of balloon area gets set in the loop above
+        * to be past the last E820 region. */
+       if (xen_initial_domain() && (xen_extra_mem[0].start < (1ULL<<32)))
+               xen_extra_mem[0].start = (1ULL<<32);
 
        /*
         * In domU, the ISA region is normal, usable memory, but we
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 5814022..996cf65 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -555,11 +555,35 @@ void free_xenballooned_pages(int nr_pages, struct page** 
pages)
 }
 EXPORT_SYMBOL(free_xenballooned_pages);
 
-static int __init balloon_init(void)
+static void __init balloon_add_memory_region(unsigned long start_pfn, unsigned 
long pages)
 {
-       domid_t domid = DOMID_SELF;
        unsigned long pfn, extra_pfn_end;
        struct page *page;
+
+       /*
+        * Initialise the balloon with excess memory space.  We need
+        * to make sure we don't add memory which doesn't exist or
+        * logically exist.  The E820 map can be trimmed to be smaller
+        * than the amount of physical memory due to the mem= command
+        * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
+        * on a system with memory which requires highmem to access,
+        * don't try to use it.
+        */
+       extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
+                           start_pfn + pages);
+       for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
+               page = pfn_to_page(pfn);
+               /* totalram_pages and totalhigh_pages do not
+                  include the boot-time balloon extension, so
+                  don't subtract from it. */
+               __balloon_append(page);
+       }
+}
+
+static int __init balloon_init(void)
+{
+       domid_t domid = DOMID_SELF;
+       int i;
        int ret;
 
        if (!xen_domain())
@@ -588,25 +612,10 @@ static int __init balloon_init(void)
        register_memory_notifier(&xen_memory_nb);
 #endif
 
-       /*
-        * Initialise the balloon with excess memory space.  We need
-        * to make sure we don't add memory which doesn't exist or
-        * logically exist.  The E820 map can be trimmed to be smaller
-        * than the amount of physical memory due to the mem= command
-        * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
-        * on a system with memory which requires highmem to access,
-        * don't try to use it.
-        */
-       extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
-                           (unsigned long)PFN_DOWN(xen_extra_mem_start + 
xen_extra_mem_size));
-       for (pfn = PFN_UP(xen_extra_mem_start);
-            pfn < extra_pfn_end;
-            pfn++) {
-               page = pfn_to_page(pfn);
-               /* totalram_pages and totalhigh_pages do not include the 
boot-time
-                  balloon extension, so don't subtract from it. */
-               __balloon_append(page);
-       }
+       for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
+               if (xen_extra_mem[i].size)
+                       
balloon_add_memory_region(PFN_UP(xen_extra_mem[i].start),
+                                                 
PFN_DOWN(xen_extra_mem[i].size));
 
        return 0;
 }
diff --git a/include/xen/page.h b/include/xen/page.h
index 0be36b9..b432c03 100644
--- a/include/xen/page.h
+++ b/include/xen/page.h
@@ -3,6 +3,13 @@
 
 #include <asm/xen/page.h>
 
-extern phys_addr_t xen_extra_mem_start, xen_extra_mem_size;
+struct xen_memory_region {
+       phys_addr_t start;
+       phys_addr_t size;
+};
+
+#define XEN_EXTRA_MEM_MAX_REGIONS 128 /* == E820MAX */
+
+extern struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS];
 
 #endif /* _XEN_PAGE_H */
-- 
1.7.2.5


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