[Xen-changelog] [xen stable-4.10] xen/pvh: do not mark the low 1MB as IO mem

[patchbot@xxxxxxx]

commit 4ba6447e7ddbee91c3781c2630ca1d28e080857c
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Jan 11 11:41:18 2018 +0000
Commit:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
CommitDate: Fri Jan 12 15:45:38 2018 +0000

    xen/pvh: do not mark the low 1MB as IO mem
    
    On PVH there's nothing special on the low 1MB.
    
    This is an optional patch that doesn't affect the functionality of the
    shim.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/mm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 0569342200..371c764027 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -122,6 +122,7 @@
 #include <asm/fixmap.h>
 #include <asm/io_apic.h>
 #include <asm/pci.h>
+#include <asm/guest.h>
 
 #include <asm/hvm/grant_table.h>
 #include <asm/pv/grant_table.h>
@@ -288,8 +289,12 @@ void __init arch_init_memory(void)
     dom_cow = domain_create(DOMID_COW, DOMCRF_dummy, 0, NULL);
     BUG_ON(IS_ERR(dom_cow));
 
-    /* First 1MB of RAM is historically marked as I/O. */
-    for ( i = 0; i < 0x100; i++ )
+    /*
+     * First 1MB of RAM is historically marked as I/O.  If we booted PVH,
+     * reclaim the space.  Irrespective, leave MFN 0 as special for the sake
+     * of 0 being a very common default value.
+     */
+    for ( i = 0; i < (pvh_boot ? 1 : 0x100); i++ )
         share_xen_page_with_guest(mfn_to_page(_mfn(i)),
                                   dom_io, XENSHARE_writable);
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.10

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