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This is not a s/r or lm specific issue. For
example, system time can be changed even when pv guest is
running. Your patch only hacks restore point once, and wc_sec can still be
changed later when system time is changed on-the-fly again.
IIRC, pv guest can catch up wall clock change in timer
interrupt, and time_resume will sync internal processed system time with new
system time after restored. But I'm not sure whether it's enough. Actually the
more interesting is the uptime difference. For example, timer with expiration
calculated on previous system time may wait nearly infinite if uptime among two
boxes vary a lot. But I think such issue should have been considered already,
e.g. some user tool assistance. I think Keir can comment better
here.
BTW, do you happen to know what exactly dom0 hangs on? In
some busy loop to catch up time, or long delay to some critical timer
expiration?
Thanks,
Kevin
Hi,
I find PV domin hung, When we take those steps
1, save PV domain
2, change system time of
PV domain back
3, restore
a PV domain
or
1, migrate a PV domain
from Machine A to Machine B
2, the system
time of Machine B is slower than Machine A.
the problem is
wc_sec will be change when system-time chanaged in dom0 or restore in a
slower-system-time machine, but when restoring, xen don't restore the wc_sec
of share_info from xenstore and use native one. So guest os will hang.
this patch will work for this issue.
Thanks
-- Song
Wei
diff -r a5ed0dbc829f tools/libxc/xc_domain_restore.c
---
a/tools/libxc/xc_domain_restore.c Tue Nov 18 14:34:14 2008
+0800
+++ b/tools/libxc/xc_domain_restore.c Fri Nov 21
17:34:15 2008 +0800
@@ -328,6 +328,16
@@
/* For info only
*/
nr_pfns = 0;
+
//jsong@xxxxxxxxxx, james song
+ memset(&domctl, 0,
sizeof(domctl));
+ domctl.domain =
dom;
+ domctl.cmd =
XEN_DOMCTL_restoredomain;
+ frc = do_domctl(xc_handle,
&domctl);
+ if ( frc != 0 )
+
{
+
ERROR("Unable to set flag of
restore.");
+
goto out;
+ }
if (
read_exact(io_fd, &p2m_size, sizeof(unsigned long))
)
{
@@ -1120,6 +1130,8
@@
/* restore saved vcpu_info and arch
specific info */
MEMCPY_FIELD(new_shared_info,
old_shared_info, vcpu_info);
+
MEMCPY_FIELD(new_shared_info, old_shared_info,
wc_nsec);
+ MEMCPY_FIELD(new_shared_info,
old_shared_info, wc_sec);
MEMCPY_FIELD(new_shared_info, old_shared_info,
arch);
/* clear any pending events and
the selector */
diff -r a5ed0dbc829f xen/arch/x86/time.c
---
a/xen/arch/x86/time.c Tue Nov 18 14:34:14 2008 +0800
+++
b/xen/arch/x86/time.c Fri Nov 21 17:34:15 2008 +0800
@@
-689,7 +689,6 @@
wmb();
(*version)++;
}
-
void
update_vcpu_system_time(struct vcpu *v)
{
struct cpu_time *t;
@@ -703,7 +702,6
@@
if ( u->tsc_timestamp ==
t->local_tsc_stamp )
return;
-
version_update_begin(&u->version);
u->tsc_timestamp = t->local_tsc_stamp;
@@
-713,14 +711,19 @@
version_update_end(&u->version);
}
-
void
update_domain_wallclock_time(struct domain
*d)
{
spin_lock(&wc_lock);
+ if(d->after_restore
)
+ {
+
d->after_restore = 0;
+ goto
out; //jsong@xxxxxxxxxx
+ }
version_update_begin(&shared_info(d,
wc_version));
shared_info(d, wc_sec) =
wc_sec + d->time_offset_seconds;
shared_info(d,
wc_nsec) = wc_nsec;
version_update_end(&shared_info(d,
wc_version));
+out:
spin_unlock(&wc_lock);
}
@@ -751,7 +754,6
@@
u64 x;
u32 y,
_wc_sec, _wc_nsec;
struct domain
*d;
-
x = (secs * 1000000000ULL) + (u64)nsecs -
system_time_base;
y = do_div(x,
1000000000);
@@ -1050,7 +1052,6 @@
struct tm
wallclock_time(void)
{
uint64_t
seconds;
-
if ( !wc_sec
)
return (struct tm) { 0
};
diff -r a5ed0dbc829f xen/common/domctl.c
---
a/xen/common/domctl.c Tue Nov 18 14:34:14 2008 +0800
+++
b/xen/common/domctl.c Fri Nov 21 17:34:15 2008 +0800
@@
-24,7 +24,6 @@
#include <asm/current.h>
#include
<public/domctl.h>
#include
<xsm/xsm.h>
-
extern long
arch_do_domctl(
struct xen_domctl *op,
XEN_GUEST_HANDLE(xen_domctl_t) u_domctl);
@@ -315,6 +314,16
@@
ret =
0;
}
break;
+ case XEN_DOMCTL_restoredomain:
+
{
+ struct domain
*d;
+ if ( (d =
rcu_lock_domain_by_id(op->domain)) == NULL
)
+
break;
+
+ d->after_restore =
1;
+
rcu_unlock_domain(d);
+
break;
+ }
case
XEN_DOMCTL_createdomain:
{
diff -r a5ed0dbc829f
xen/include/public/domctl.h
---
a/xen/include/public/domctl.h Tue Nov 18 14:34:14 2008
+0800
+++ b/xen/include/public/domctl.h Fri Nov 21
17:34:15 2008 +0800
@@ -61,6 +61,7 @@
#define
XEN_DOMCTL_destroydomain 2
#define
XEN_DOMCTL_pausedomain
3
#define XEN_DOMCTL_unpausedomain
4
+#define XEN_DOMCTL_restoredomain
51
#define XEN_DOMCTL_resumedomain
27
#define
XEN_DOMCTL_getdomaininfo 5
diff -r
a5ed0dbc829f xen/include/xen/sched.h
---
a/xen/include/xen/sched.h Tue Nov 18 14:34:14 2008
+0800
+++ b/xen/include/xen/sched.h Fri Nov 21 17:34:15
2008 +0800
@@ -231,6 +231,7 @@
* cause a
deadlock. Acquirers don't spin waiting; they
preempt.
*/
spinlock_t hypercall_deadlock_mutex;
+ int after_restore;
//jsong@xxxxxxxxxx
};
struct
domain_setup_info
---------------------------------------------------------------------------------------------
Thanks
--Song
wei
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