tools/migrate: Prevent PTE truncation from being fatal duing the live phase

It is possible, when normalising a PV pagetable that the table has been freed
and reused for something else by the guest.

In such a case, data read might no longer be a pagetable, and fail the
truncation check.  However, this should only be fatal if we encounter such a
page in the paused phase.

This check is now consistent with all other checks in the same area.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/tools/libxc/xc_sr_save_x86_pv.c b/tools/libxc/xc_sr_save_x86_pv.c
index 7043409231935e36e1b2dd1c840adc993cc1b5e8..f218d17bce01e2e5a0a42cb2b088a24f19e7c259 100644 (file)
--- a/tools/libxc/xc_sr_save_x86_pv.c
+++ b/tools/libxc/xc_sr_save_x86_pv.c
@@ -949,9 +949,14 @@ static int normalise_pagetable(struct xc_sr_context *ctx, const uint64_t *src,
 #ifdef __i386__
             if ( mfn == INVALID_MFN )
             {
-                ERROR("PTE truncation detected.  L%lu[%u] = %016"PRIx64,
-                      type >> XEN_DOMCTL_PFINFO_LTAB_SHIFT, i, pte);
-                errno = E2BIG;
+                if ( !ctx->dominfo.paused )
+                    errno = EAGAIN;
+                else
+                {
+                    ERROR("PTE truncation detected.  L%lu[%u] = %016"PRIx64,
+                          type >> XEN_DOMCTL_PFINFO_LTAB_SHIFT, i, pte);
+                    errno = E2BIG;
+                }
                 return -1;
             }
 #endif