[PATCH 26/27] Enable 32bit dirty log pointers on 64bit host

[Alexander Graf <agraf@suse.de>]

With big endian userspace, we can't quite figure out if a pointer
is 32 bit (shifted >> 32) or 64 bit when we read a 64 bit pointer.

This is what happens with dirty logging. To get the pointer interpreted
correctly, I just make it bounce twice, but admittedly that is not ideal.

I'm open for suggestions here.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 virt/kvm/kvm_main.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e27b7a9..91c0225 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -720,6 +720,11 @@ int kvm_get_dirty_log(struct kvm *kvm,
 
 	r = -EFAULT;
 	if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))
+#ifdef __BIG_ENDIAN
+		/* Did we get a 32 bit pointer? */
+		if (copy_to_user((void*)((u64)log->dirty_bitmap >> 32),
+				 memslot->dirty_bitmap, n))
+#endif
 		goto out;
 
 	if (any)
-- 
1.6.0.2