Re: Subject: Re: port-xen/45975: panic: HYPERVISOR_mmu_update failed, ret: -22 on -current MP domU (amd64)

[Cherry G. Mathew <cherry%zyx.in@localhost>]

The following reply was made to PR port-xen/45975; it has been noted by GNATS.

From: Cherry G. Mathew <cherry%zyx.in@localhost>
To: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
Cc: gnats-bugs%NetBSD.org@localhost,  port-xen-maintainer%NetBSD.org@localhost, 
 gnats-admin%NetBSD.org@localhost,  netbsd-bugs%NetBSD.org@localhost
Subject: Re: Subject: Re: port-xen/45975: panic: HYPERVISOR_mmu_update failed, 
ret: -22 on -current MP domU (amd64)
Date: Wed, 15 Feb 2012 00:49:38 +0530

 >>>>> Manuel Bouyer <bouyer%antioche.eu.org@localhost> writes:
 
     >> On Tue, Feb 14, 2012 at 11:41:02PM +0530, Cherry G. Mathew wrote:
 
 [...]
 
     >> Isn't a tlb shootdown needed after this, to make sure the old pte
     >> is not referred to in the TLB ?
 
     >> The pmap code does it. Plus, I suspect that the hypervisor does
     >> tlb flushes itself, to make sure you can't write accidentally to
     >> a ptp page using stale TLB entries.
 
     >> 
     >> Separately, please note that the tlb shootdown code ignores
     >> requests to shootdown when the pmap is being destroyed.
 
     >> this shouldn't be a problem.
 
 Perhaps - but if there's a stale entry pointing to the now destroyed
 pmap pdir....
 
 Incidentally, it looks like dom0 with MP hits this bug/symptom at boot -
 might be easier to trigger + debug. (I don't have a dom0 setup handy).
 
 Cheers,
 -- 
 Cherry