[Xen-devel] [PATCH 2/5] x86/dom0: allow stealing RAM from a region that starts in the low 1MB

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

As long as the memory stolen is always above 1MB. This allows the PVH
Dom0 builder to be used on a memory map that only has a single RAM
region starting at 0.

Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/arch/x86/hvm/dom0_build.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index 91dc27dc3e..24cc15f28b 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -154,12 +154,13 @@ static int __init pvh_steal_ram(struct domain *d, 
unsigned long size,
     {
         struct e820entry *entry = &d->arch.e820[i];
 
-        if ( entry->type != E820_RAM || entry->addr + entry->size > limit ||
-             entry->addr < MB(1) )
+        if ( entry->type != E820_RAM || entry->addr + entry->size > limit )
             continue;
 
         *addr = (entry->addr + entry->size - size) & ~(align - 1);
-        if ( *addr < entry->addr )
+        if ( *addr < entry->addr ||
+             /* Don't steal from the low 1MB due to the copying done there. */
+             *addr < MB(1) )
             continue;
 
         entry->size = *addr - entry->addr;
-- 
2.17.2 (Apple Git-113)


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