From mboxrd@z Thu Jan  1 00:00:00 1970
From: toshi.kani@hpe.com (Kani, Toshi)
Date: Sat, 28 Apr 2018 20:54:42 +0000
Subject: [PATCH v2 2/2] x86/mm: implement free pmd/pte page interfaces
In-Reply-To: <20180428090217.n2l3w4vobmtkvz6k@8bytes.org>
References: <20180314180155.19492-1-toshi.kani@hpe.com>
 <20180314180155.19492-3-toshi.kani@hpe.com>
 <20180426141926.GN15462@8bytes.org> <1524759629.2693.465.camel@hpe.com>
 <20180426172327.GQ15462@8bytes.org> <1524764948.2693.478.camel@hpe.com>
 <20180426200737.GS15462@8bytes.org> <1524781764.2693.503.camel@hpe.com>
 <20180427073719.GT15462@8bytes.org> <1524839460.2693.531.camel@hpe.com>
 <20180428090217.n2l3w4vobmtkvz6k@8bytes.org>
Message-ID: <1524948829.2693.547.camel@hpe.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Sat, 2018-04-28 at 11:02 +0200, joro at 8bytes.org wrote:
> On Fri, Apr 27, 2018 at 02:31:51PM +0000, Kani, Toshi wrote:
> > So, we can add the step 2 on top of this patch.
> >  1. Clear pud/pmd entry.
> >  2. System wide TLB flush <-- TO BE ADDED BY NEW PATCH
> >  3. Free its underlining pmd/pte page.
> 
> This still lacks the page-table synchronization and will thus not fix
> the BUG_ON being triggered.

The BUG_ON issue is specific to PAE that it syncs at the pmd level.
x86/64 does not have this issue since it syncs at the pgd or p4d level.

> > We do not need to revert this patch.  We can make the above change I
> > mentioned.
> 
> Please note that we are not in the merge window anymore and that any fix
> needs to be simple and obviously correct.

Understood.  Changing the x86/32 sync point is risky.  So, I am going to
revert the free page handling for PAE.   

Thanks,
-Toshi