tools/init-xenstore-domain: fix memory map for PVH stubdom

In case of maxmem != memsize the E820 map of the PVH stubdom is wrong,
as it is missing the RAM above memsize.

Additionally the memory map should only specify the Xen special pages
as reserved.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
master commit: 134d53f577
master date: 2022-07-12 15:25:20 +0200

tools/helpers/init-xenstore-domain.c

@@ -72,8 +72,9 @@ static int build(xc_interface *xch)
     char cmdline[512];
     int rv, xs_fd;
     struct xc_dom_image *dom = NULL;
-    int limit_kb = (maxmem ? : (memory + 1)) * 1024;
+    int limit_kb = (maxmem ? : memory) * 1024 + X86_HVM_NR_SPECIAL_PAGES * 4;
     uint64_t mem_size = MB(memory);
+    uint64_t max_size = MB(maxmem ? : memory);
     struct e820entry e820[3];
     struct xen_domctl_createdomain config = {
         .ssidref = SECINITSID_DOMU,
@@ -166,13 +167,16 @@ static int build(xc_interface *xch)
         dom->mmio_start = LAPIC_BASE_ADDRESS;
         dom->max_vcpus = 1;
         e820[0].addr = 0;
-        e820[0].size = dom->lowmem_end;
+        e820[0].size = (max_size > LAPIC_BASE_ADDRESS) ?
+                       LAPIC_BASE_ADDRESS : max_size;
         e820[0].type = E820_RAM;
-        e820[1].addr = LAPIC_BASE_ADDRESS;
-        e820[1].size = dom->mmio_size;
+        e820[1].addr = (X86_HVM_END_SPECIAL_REGION -
+                        X86_HVM_NR_SPECIAL_PAGES) << XC_PAGE_SHIFT;
+        e820[1].size = X86_HVM_NR_SPECIAL_PAGES << XC_PAGE_SHIFT;
         e820[1].type = E820_RESERVED;
         e820[2].addr = GB(4);
-        e820[2].size = dom->highmem_end - GB(4);
+        e820[2].size = (max_size > LAPIC_BASE_ADDRESS) ?
+                       max_size - LAPIC_BASE_ADDRESS : 0;
         e820[2].type = E820_RAM;
     }