[Xen-devel] [PATCH] xen/dom0: Use host E820 map

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Ian Campbell <ian.campbell@xxxxxxxxxx>

Unlike the non-paravirt Xen port we do not have distinct psuedo-physical
and I/O memory resource-spaces and therefore resources in the two
can clash. Fix this by registering a memory map which matches the
underlying I/O map. Currently this wastes the memory in the reserved
regions. Eventually we should remap this memory to the end of the
address space.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/xen/setup.c           |   45 +++++++++++++++++++++++++++++++++++++--
 include/xen/interface/memory.h |   29 +++++++++++++++++++++++++
 2 files changed, 71 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 3e4cf46..175396c 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -19,6 +19,7 @@
 
 #include <xen/page.h>
 #include <xen/interface/callback.h>
+#include <xen/interface/memory.h>
 #include <xen/interface/physdev.h>
 #include <xen/features.h>
 
@@ -36,16 +37,54 @@ extern void xen_syscall32_target(void);
 /**
  * machine_specific_memory_setup - Hook for machine specific memory setup.
  **/
-
 char * __init xen_memory_setup(void)
 {
        unsigned long max_pfn = xen_start_info->nr_pages;
+       unsigned long long mem_end;
+       int rc;
+       struct xen_memory_map memmap;
+       /*
+        * This is rather large for a stack variable but this early in
+        * the boot process we know we have plenty slack space.
+        */
+       struct e820entry map[E820MAX];
+       int op = xen_initial_domain() ?
+               XENMEM_machine_memory_map :
+               XENMEM_memory_map;
+       int i;
 
        max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);
+       mem_end = PFN_PHYS((u64)max_pfn);
+
+       memmap.nr_entries = E820MAX;
+       set_xen_guest_handle(memmap.buffer, map);
+
+       rc = HYPERVISOR_memory_op(op, &memmap);
+       if (rc == -ENOSYS) {
+               memmap.nr_entries = 1;
+               map[0].addr = 0ULL;
+               map[0].size = mem_end;
+               /* 8MB slack (to balance backend allocations). */
+               map[0].size += 8ULL << 20;
+               map[0].type = E820_RAM;
+               rc = 0;
+       }
+       BUG_ON(rc);
 
        e820.nr_map = 0;
-
-       e820_add_region(0, PFN_PHYS((u64)max_pfn), E820_RAM);
+       for (i = 0; i < memmap.nr_entries; i++) {
+               unsigned long long end = map[i].addr + map[i].size;
+               if (map[i].type == E820_RAM) {
+                       if (map[i].addr > mem_end)
+                               continue;
+                       if (end > mem_end) {
+                               /* Truncate region to max_mem. */
+                               map[i].size -= end - mem_end;
+                       }
+               }
+               if (map[i].size > 0)
+                       e820_add_region(map[i].addr, map[i].size, map[i].type);
+       }
 
        /*
         * Even though this is normal, usable memory under Xen, reserve
diff --git a/include/xen/interface/memory.h b/include/xen/interface/memory.h
index af36ead..e6c6bcb 100644
--- a/include/xen/interface/memory.h
+++ b/include/xen/interface/memory.h
@@ -142,4 +142,33 @@ struct xen_translate_gpfn_list {
 };
 DEFINE_GUEST_HANDLE_STRUCT(xen_translate_gpfn_list);
 
+/*
+ * Returns the pseudo-physical memory map as it was when the domain
+ * was started (specified by XENMEM_set_memory_map).
+ * arg == addr of struct xen_memory_map.
+ */
+#define XENMEM_memory_map           9
+struct xen_memory_map {
+    /*
+     * On call the number of entries which can be stored in buffer. On
+     * return the number of entries which have been stored in
+     * buffer.
+     */
+    unsigned int nr_entries;
+
+    /*
+     * Entries in the buffer are in the same format as returned by the
+     * BIOS INT 0x15 EAX=0xE820 call.
+     */
+    GUEST_HANDLE(void) buffer;
+};
+DEFINE_GUEST_HANDLE_STRUCT(xen_memory_map);
+
+/*
+ * Returns the real physical memory map. Passes the same structure as
+ * XENMEM_memory_map.
+ * arg == addr of struct xen_memory_map.
+ */
+#define XENMEM_machine_memory_map   10
+
 #endif /* __XEN_PUBLIC_MEMORY_H__ */
-- 
1.6.0.6


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