WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] [PATCH 08/10] xen/mmu: Bugfix. Fill the top entry page with

To: linux-kernel@xxxxxxxxxxxxxxx, jeremy@xxxxxxxx, hpa@xxxxxxxxx
Subject: [Xen-devel] [PATCH 08/10] xen/mmu: Bugfix. Fill the top entry page with appropriate middle layer pointers.
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Tue, 21 Dec 2010 16:37:38 -0500
Cc: Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Jan Beulich <JBeulich@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Delivery-date: Tue, 21 Dec 2010 13:40:02 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <1292967460-15709-1-git-send-email-konrad.wilk@xxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <1292967460-15709-1-git-send-email-konrad.wilk@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
If we swapped over from using an p2m_mid_identical to p2m_mid_missing
(earlier call to set_phys_to_machine) and then started going through the
PFNs in descending order to program a new MFN (balloon worker), we would
end up in this code path. At that point we would set up new page filled with
pointers to p2m_identity instead of p2m_missing. This had the disastrous
effect that get_phys_to_machine on that PFN would return an 1-1 mapping
instead of INVALID_P2M_ENTRY resulting in hitting a BUG check in balloon driver.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/mmu.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 92f4fec..a917439 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -480,7 +480,10 @@ static bool alloc_p2m(unsigned long pfn)
                if (!mid)
                        return false;
 
-               p2m_mid_init(mid, p2m_identity);
+               if (mid == p2m_mid_identity)
+                       p2m_mid_init(mid, p2m_identity);
+               else
+                       p2m_mid_init(mid, p2m_missing);
 
                if (cmpxchg(top_p, mid_orig, mid) != mid_orig)
                        free_p2m_page(mid);
-- 
1.7.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel