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Message-ID: <1370087051.3766.40.camel@pasglop>
Subject: Re: [PATCH] powerpc/mm: Always invalidate tlb on hpte invalidate
 and update
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Michael Ellerman <michael@ellerman.id.au>
Date: Sat, 01 Jun 2013 21:44:11 +1000
In-Reply-To: <20130601111908.GA16571@concordia>
References: <1369998204-31490-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
 <20130601111908.GA16571@concordia>
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Cc: linuxppc-dev@lists.ozlabs.org,
 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
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On Sat, 2013-06-01 at 21:19 +1000, Michael Ellerman wrote:
> On Fri, May 31, 2013 at 04:33:24PM +0530, Aneesh Kumar K.V wrote:
> > From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
> > 
> > If a hash bucket gets full, we "evict" a more/less random entry from it.
> > When we do that we don't invalidate the TLB (hpte_remove) because we assume
> > the old translation is still technically "valid". This implies that when
> > we are invalidating or updating pte, even if HPTE entry is not valid
> > we should do a tlb invalidate.
> > 
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> 
> Has this always been a bug? I assume not.
> 
> I'm asking because I have a kernel that's crashing and I'm wondering if
> I might need this commit.

Bug got introduced in either 
b1022fbd293564de91596b8775340cf41ad5214c or
7e74c3921ad9610c0b49f28b8fc69f7480505841, the jury is still out on
that one :-)

It's unlikely to crash the kernel however (it *can*, it's just unlikely).

Patch is good to have regardless...

Cheers,
Ben.