From owner-freebsd-arm@FreeBSD.ORG  Fri Jul 10 08:27:07 2009
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Date: Fri, 10 Jul 2009 10:27:30 +0200
From: Michal Hajduk <mih@semihalf.com>
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To: Mark Tinguely <tinguely@casselton.net>
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Cc: freebsd-arm@freebsd.org
Subject: Re: pmap problem in FreeBSD current
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Hi Mark,
We've diagnosed the problem and it was related to arm_nocache_remap().
When the page was remaped into non-cacheable virtual memory region
there was no dcache write-back operation, so count of free items in
slab had differ value then should had.
This write-back operation should have been done in pmap_set_cache_entry()
but PVF_REF flag was missing so this part of code was omitted.

I think that we should enable PVF_REF flag in pmap_enter_pv().

================================================

diff --git a/sys/arm/arm/pmap.c b/sys/arm/arm/pmap.c
index 3cdab65..133dc6d 100644
--- a/sys/arm/arm/pmap.c
+++ b/sys/arm/arm/pmap.c
@@ -1683,7 +1683,7 @@ pmap_enter_pv(struct vm_page *pg, struct pv_entry 
*pve, pmap_t pm,
/* PMAP_ASSERT_LOCKED(pmap_kernel()); */
pve->pv_pmap = pmap_kernel();
pve->pv_va = pg->md.pv_kva;
- pve->pv_flags = PVF_WRITE | PVF_UNMAN;
+ pve->pv_flags = PVF_WRITE | PVF_UNMAN | PVF_REF;
pg->md.pv_kva = 0;

TAILQ_INSERT_HEAD(&pg->md.pv_list, pve, pv_list);

=================================================

With this patch I've had no panics.

Many thanks,
Michał Hajduk