From: Roger Pau Monne <roger.pau@citrix.com>
Date: Thu, 11 Jan 2018 11:41:18 +0000 (+0000)
Subject: xen/pvh: do not mark the low 1MB as IO mem
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~786
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=01fe63ce354f5e3c2f42cc35b76fcab2f400fd93;p=xen.git

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@citrix.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index a21a668d73..1147a1afb1 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);