[Xen-devel] [PATCH 4/5] xen: Fix the memory registration to reflect of what is done by Xen.

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

A Xen guest memory is allocated by libxc. But this memory is not
allocated continuously, instead, it leaves the VGA IO memory space not
allocated, same for the MMIO space (at HVM_BELOW_4G_MMIO_START of size
HVM_BELOW_4G_MMIO_LENGTH).

So to reflect that, we do not register the physical memory for this two
holes. But we still keep only one RAMBlock for the all RAM as it is more
easier than have two separate blocks (1 above 4G). Also this prevent QEMU
from use the MMIO space for a ROM.

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 xen-all.c |   21 ++++++++++++++-------
 1 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/xen-all.c b/xen-all.c
index 2c0a62d..76d5c5c 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -144,6 +144,12 @@ static void xen_ram_init(ram_addr_t ram_size)
     new_block->host = NULL;
     new_block->offset = 0;
     new_block->length = ram_size;
+    if (ram_size >= HVM_BELOW_4G_RAM_END) {
+        /* Xen does not allocate the memory continuously, and keep a hole at
+         * HVM_BELOW_4G_MMIO_START of HVM_BELOW_4G_MMIO_LENGTH
+         */
+        new_block->length += HVM_BELOW_4G_MMIO_LENGTH;
+    }
 
     QLIST_INSERT_HEAD(&ram_list.blocks, new_block, next);
 
@@ -152,20 +158,21 @@ static void xen_ram_init(ram_addr_t ram_size)
     memset(ram_list.phys_dirty + (new_block->offset >> TARGET_PAGE_BITS),
            0xff, new_block->length >> TARGET_PAGE_BITS);
 
-    if (ram_size >= 0xe0000000 ) {
-        above_4g_mem_size = ram_size - 0xe0000000;
-        below_4g_mem_size = 0xe0000000;
+    if (ram_size >= HVM_BELOW_4G_RAM_END) {
+        above_4g_mem_size = ram_size - HVM_BELOW_4G_RAM_END;
+        below_4g_mem_size = HVM_BELOW_4G_RAM_END;
     } else {
         below_4g_mem_size = ram_size;
     }
 
-    cpu_register_physical_memory(0, below_4g_mem_size, new_block->offset);
-#if TARGET_PHYS_ADDR_BITS > 32
+    cpu_register_physical_memory(0, 0xa0000, 0);
+    /* Skip of the VGA IO memory space */
+    cpu_register_physical_memory(0xc0000, below_4g_mem_size - 0xc0000,
+                                 0xc0000);
     if (above_4g_mem_size > 0) {
         cpu_register_physical_memory(0x100000000ULL, above_4g_mem_size,
-                                     new_block->offset + below_4g_mem_size);
+                                     0x100000000ULL);
     }
-#endif
 }
 
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size)
-- 
Anthony PERARD


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