[Xen-ia64-devel] [PATCH] Fix domain reboot bug

["Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>]

Actually domain reboot issue is not caused by our previous patch to
solve schedule_tail, which instead helps to find a severe HOST_SMP plus
domain destroy bug.

The major reason is that currently VHPT table for dom0/domU is per LP,
while domain destroy only issues vhpt_flush on current LP (dom0 is
running). So VHPT table is not flushed on the LP that destroyed domU is
running. 

The mechanism of domain reboot is to kill current domain and create a
new domain with same configuration. Since region id recycle is added
last time with domain destroy support, the new created domain will
inherit same region id as previous one. Under this case, the stale
entries in VHPT table will make new domU halt.

Before applying our schedule_tail patch, domU will keep same pta value
as idle domain when first created where vhpt walker is disabled. Because
we use bvt as default scheduler, context switch never happens as long as
domU is runnable. That means domU will have vhpt DISABLED in whole life
cycle. So even vhpt on that LP is not flushed, domU still runs
correctly.

So we need to send IPI to target LP to flush right vhpt table.
Especially, based on our previous patch for schedule_tail, domU can get
performance gain by enabling vhpt walker.

Best & Regards 

- Kevin & Xiantao

Attachment: fix_reboot_bug_with_vhpt_enable.patch
Description: fix_reboot_bug_with_vhpt_enable.patch

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