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

[David Vrabel <david.vrabel@citrix.com>]

From: David Vrabel <david.vrabel@citrix.com>

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_memory_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@citrix.com>
---
 arch/x86/xen/setup.c  |   20 ++++++++++----------
 drivers/xen/balloon.c |   44 +++++++++++++++++++++++++++-----------------
 include/xen/page.h    |   10 +++++++++-
 3 files changed, 46 insertions(+), 28 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c983717..0c8e974 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;
 
 /* Number of pages released from the initial allocation. */
 unsigned long xen_released_pages;
@@ -59,7 +59,7 @@ 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;
@@ -69,7 +69,7 @@ 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);
 
@@ -242,7 +242,7 @@ 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;
 
@@ -270,8 +270,8 @@ 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)
@@ -279,10 +279,10 @@ 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 9efb993..fc43b53 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -555,11 +555,32 @@ 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_region(unsigned long start_pfn,
+				      unsigned long pages)
 {
 	unsigned long pfn, extra_pfn_end;
 	struct page *page;
 
+	/*
+	 * If the amount of usable memory has been limited (e.g., with
+	 * the 'mem' command line parameter), don't add pages beyond
+	 * this limit.
+	 */
+	extra_pfn_end = min(max_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)
+{
+	int i;
+
 	if (!xen_domain())
 		return -ENODEV;
 
@@ -587,23 +608,12 @@ static int __init balloon_init(void)
 
 	/*
 	 * Initialize the balloon with pages from the extra memory
-	 * region (see arch/x86/xen/setup.c).
-	 *
-	 * If the amount of usable memory has been limited (e.g., with
-	 * the 'mem' command line parameter), don't add pages beyond
-	 * this limit.
+	 * regions (see arch/x86/xen/setup.c).
 	 */
-	extra_pfn_end = min(max_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_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 92b61f8..12765b6 100644
--- a/include/xen/page.h
+++ b/include/xen/page.h
@@ -3,7 +3,15 @@
 
 #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 __initdata
+struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS];
 
 extern unsigned long xen_released_pages;
 
-- 
1.7.2.5