[Xen-devel] [RFC Patch v4 13/18] tools: xc_doamin_restore: zero ioreq page only one time

[Wen Congyang <wency@xxxxxxxxxxxxxx>]

ioreq page contains evtchn which will be set when we resume the
secondary vm the first time. The hypervisor will check if the
evtchn is corrupted, so we cannot zero the ioreq page more
than one time.

The ioreq->state is always STATE_IOREQ_NONE after the vm is
suspended, so it is OK if we only zero it one time.
---
 tools/libxc/xc_domain_restore.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/tools/libxc/xc_domain_restore.c b/tools/libxc/xc_domain_restore.c
index c7ef39f..497dadb 100644
--- a/tools/libxc/xc_domain_restore.c
+++ b/tools/libxc/xc_domain_restore.c
@@ -1501,6 +1501,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, 
uint32_t dom,
     struct restore_ctx _ctx;
     struct restore_ctx *ctx = &_ctx;
     struct domain_info_context *dinfo = &ctx->dinfo;
+    int skip_clear_ioreq_page = 0;
 
     DPRINTF("%s: starting restore of new domid %u", __func__, dom);
 
@@ -2331,13 +2332,30 @@ new_checkpoint:
     }
 
     /* These comms pages need to be zeroed at the start of day */
-    if ( xc_clear_domain_page(xch, dom, tailbuf.u.hvm.magicpfns[0]) ||
-         xc_clear_domain_page(xch, dom, tailbuf.u.hvm.magicpfns[1]) ||
-         xc_clear_domain_page(xch, dom, tailbuf.u.hvm.magicpfns[2]) )
+    if ( xc_clear_domain_page(xch, dom, tailbuf.u.hvm.magicpfns[2]) )
     {
         PERROR("error zeroing magic pages");
         goto out;
     }
+    if ( !skip_clear_ioreq_page )
+    {
+        if ( xc_clear_domain_page(xch, dom, tailbuf.u.hvm.magicpfns[0]) ||
+             xc_clear_domain_page(xch, dom, tailbuf.u.hvm.magicpfns[1]) )
+        {
+            PERROR("error zeroing magic pages");
+            goto out;
+        }
+        /*
+         * ioreq page contains evtchn which will be set when we resume the
+         * secondary vm the first time. The hypervisor will check if the
+         * evtchn is corrupted, so we cann't clear the ioreq page more
+         * than one time.
+         *
+         * The ioreq->state is always STATE_IOREQ_NONE after the vm is
+         * suspended, so it is OK if we only clear it one time.
+         */
+        skip_clear_ioreq_page = 1;
+    }
 
     if ( (frc = xc_hvm_param_set(xch, dom,
                                  HVM_PARAM_IOREQ_PFN, 
tailbuf.u.hvm.magicpfns[0]))
-- 
1.9.3


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