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

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH 3/5] xen: allow balloon driver to use more than one memory region
From: David Vrabel <david.vrabel@xxxxxxxxxx>
Date: Fri, 19 Aug 2011 15:57:18 +0100
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Delivery-date: Fri, 19 Aug 2011 08:10:52 -0700
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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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