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RE: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up tim

To: "Du, Hang" <hdu@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up time from dom0 to domU
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Tue, 12 Oct 2010 08:39:28 -0700 (PDT)
Cc: "Liu, Saipu" <saliu@xxxxxxxxxxxx>, "Yi, Shunli" <syi@xxxxxxxxxxxx>
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I’m not sure what kernel tree you are proposing this against, but as I said in the previous thread, I think this is a bad idea for general use.  It is too easy for a dom0 system administrator to unwittingly wreak subtle and mysterious havoc on possibly dozens of guests each with dozens of users.  The only advantage is that it saves time for that dom0 administrator who would otherwise have to go into each guest individually and change the time (backwards, which is never recommended in any running system).


From: Du, Hang [mailto:hdu@xxxxxxxxxxxx]
Sent: Tuesday, October 12, 2010 4:19 AM
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Liu, Saipu; Yi, Shunli
Subject: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up time from dom0 to domU


Signed-off-by: Shunli Yi <shyi@xxxxxxxxxxxx>

Signed-off-by: Hang Du <hdu@xxxxxxxxxxxx>


When sync up time from dom0 to domU, the monotonic time should be reset or domU cannot sync up backward time from dom0.


diff –urN a/arch/i386/kernel/time-xen.c   b/arch/i386/kernel/time-xen.c  


--- a/arch/i386/kernel/time-xen.c   2010-10-11 10:41:06.000000000 +0800

+++ b/arch/i386/kernel/time-xen.c   2010-10-11 10:43:32.000000000 +0800

@@ -715,6 +715,8 @@



    if (shadow_tv_version != HYPERVISOR_shared_info->wc_version) {

+        if (!independent_wallclock)

+            monotonic_reset();


        schedule_clock_was_set_work = 1;




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