[Xen-changelog] [xen-unstable] x86/mm/paging: Prevent the guest from faulting on the same gfn when dying

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Tim Deegan <tim@xxxxxxx>
# Date 1331809964 0
# Node ID fa7d1e7a5fae658686f041c080b45600be797744
# Parent  1bff003ba64bd8c17eed61baebd689951cef8844
x86/mm/paging: Prevent the guest from faulting on the same gfn when dying

A crashing guest due to paging may hit an "endless" loop faulting repeatedly on
the current paged-out gfn, until the toolstack comes around to killing the
domain.

Unfortunately domain_crash at this point may not pause the vcpu due to the
shutting_down flag, so we pause it explicitly when detecting the condition.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
Acked-by: Tim Deegan <tim@xxxxxxx>
Committed-by: Tim Deegan <tim@xxxxxxx>
---


diff -r 1bff003ba64b -r fa7d1e7a5fae xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c     Thu Mar 15 11:12:44 2012 +0000
+++ b/xen/arch/x86/mm/p2m.c     Thu Mar 15 11:12:44 2012 +0000
@@ -988,6 +988,9 @@
     {
         gdprintk(XENLOG_ERR, "Domain %hu paging gfn %lx yet no ring "
                              "in place\n", d->domain_id, gfn);
+        /* Prevent the vcpu from faulting repeatedly on the same gfn */
+        if ( v->domain == d )
+            vcpu_pause_nosync(v);
         domain_crash(d);
         return;
     }

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