libxl: do slow resume after failed migration attempt

both of the current callers for libxl_domain_resume are calling after
a migration has failed, one is failure to suspend on the sender and
the other is failure to start on the destination, both leading to a
resume attempt on the sender.

However in the first case, failure to suspend, there is no guarantee
that the guest has made it as far as the suspend hypercall and
therefore the fast resume method, which frobs the hypercall return to
indicate a cancelled suspend, cannot safely be used since it will
corrupt %eax/%rax.

For the second case, failure to start on destination, I don't think it
really matters if the resume is fast or slow.

Therefore always use the slow/uncooperative version of xc_domain_resume from
libxl_domain_resume.

This makes a PV domain which failed to suspend (e.g. because the core
Linux PM infrastructure within the guest didn't allow it) recover
gracefully.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 990aa8aa249307fe7f150028f5128ea3fd8de84a..5dd936fdc24bca0e980d4240508920a4026dc05c 100644 (file)
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -226,7 +226,7 @@ int libxl_domain_resume(libxl_ctx *ctx, uint32_t domid)
         rc = ERROR_NI;
         goto out;
     }
-    if (xc_domain_resume(ctx->xch, domid, 1)) {
+    if (xc_domain_resume(ctx->xch, domid, 0)) {
         LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, 
                         "xc_domain_resume failed for domain %u", 
                         domid);