File 5321b20b-common-make-hypercall-preemption-checks-consistent.patch of Package xen.openSUSE_13.1_Update

# Commit 8c0eed2cc8d8a2ccccdffe4c386b625b672dc12a
# Date 2014-03-13 14:26:35 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
common: make hypercall preemption checks consistent

- never preempt on the first iteration (ensure forward progress)
- do cheap checks first

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>
Acked-by: Keir Fraser <keir@xen.org>

--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -59,7 +59,7 @@ static void increase_reservation(struct 
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -105,7 +105,7 @@ static void populate_physmap(struct memo
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -242,7 +242,7 @@ static void decrease_reservation(struct 
 
     for ( i = a->nr_done; i < a->nr_extents; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != a->nr_done && hypercall_preempt_check() )
         {
             a->preempted = 1;
             goto out;
@@ -365,7 +365,8 @@ static long memory_exchange(XEN_GUEST_HA
           i < (exch.in.nr_extents >> in_chunk_order);
           i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i != (exch.nr_exchanged >> in_chunk_order) &&
+             hypercall_preempt_check() )
         {
             exch.nr_exchanged = i << in_chunk_order;
             rcu_unlock_domain(d);
--- a/xen/common/multicall.c
+++ b/xen/common/multicall.c
@@ -52,7 +52,7 @@ do_multicall(
 
     for ( i = 0; !rc && i < nr_calls; i++ )
     {
-        if ( hypercall_preempt_check() )
+        if ( i && hypercall_preempt_check() )
             goto preempted;
 
         if ( unlikely(__copy_from_guest(&mcs->call, call_list, 1)) )
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -369,11 +369,11 @@ static DECLARE_SOFTIRQ_TASKLET(notify_do
 static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer, int count)
 {
     char kbuf[128], *kptr;
-    int kcount;
+    int kcount = 0;
 
     while ( count > 0 )
     {
-        if ( hypercall_preempt_check() )
+        if ( kcount && hypercall_preempt_check() )
             return hypercall_create_continuation(
                 __HYPERVISOR_console_io, "iih",
                 CONSOLEIO_write, count, buffer);