[Xen-devel] Questions about sh_prefetch and log_dirty

[David Knight <dongwei.net@xxxxxxxxxx>]

Hi,

I've been working on a project which is to minimize the
overhead of page_fault when PV is in log_dirty mode. I
wrote a function "sh_prebuild", it's very much similar
to sh_prefetch(), the major difference between them is:
I set the "ft" as "ft_demand_write" rather than
"ft_prefetch" when I call l1e_propagate_from_guest().
I just want to make the faulted page and its following
pages writable and marked as dirty after a write_protect
page_fault. The function "sh_prebuild" is called in the
sh_page_fault() right before sh_prefetch():

---------------sh_page_fault()-----------------

if ( ( shadow_mode_log_dirty(v->domain) )
&& ( ft == ft_demand_write ) )
sh_prebuild(.......);

..............

I got problems when I migrate. The code can successfully
migrate the domainU to another UNMODIFIED Xen. But when I
migrate a domainU from UNMODIFIED Xen back to this MODIFIED
Xen, the domU's clock is frozen, I use "xm console" to get
in domU's console, but I just got about 6 TSC error messages
and no other respond.

I am using 32-bit PV domain, no-PSE.
Does someone know any reasons? Thanks.



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