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From: Michal Hocko <mhocko@kernel.org>
To: "Kani, Toshi" <toshi.kani@hpe.com>
Cc: "tglx@linutronix.de" <tglx@linutronix.de>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"cpandya@codeaurora.org" <cpandya@codeaurora.org>
Subject: Re: [PATCH v3 0/3] fix free pmd/pte page handlings on x86
Date: Mon, 25 Jun 2018 19:53:12 +0200	[thread overview]
Message-ID: <20180625175225.GQ28965@dhcp22.suse.cz> (raw)
In-Reply-To: <1529938470.14039.134.camel@hpe.com>

On Mon 25-06-18 14:56:26, Kani Toshimitsu wrote:
> On Sun, 2018-06-24 at 15:19 +0200, Thomas Gleixner wrote:
> > On Wed, 16 May 2018, Toshi Kani wrote:
> > 
> > > This series fixes two issues in the x86 ioremap free page handlings
> > > for pud/pmd mappings.
> > > 
> > > Patch 01 fixes BUG_ON on x86-PAE reported by Joerg.  It disables
> > > the free page handling on x86-PAE.
> > > 
> > > Patch 02-03 fixes a possible issue with speculation which can cause
> > > stale page-directory cache.
> > >  - Patch 02 is from Chintan's v9 01/04 patch [1], which adds a new arg
> > >    'addr', with my merge change to patch 01.
> > >  - Patch 03 adds a TLB purge (INVLPG) to purge page-structure caches
> > >    that may be cached by speculation.  See the patch descriptions for
> > >    more detal.
> > 
> > Toshi, Joerg, Michal!
> 
> Hi Thomas,
> 
> Thanks for checking. I was about to ping as well.
> 
> > I'm failing to find a conclusion of this discussion. Can we finally make
> > some progress with that?
> 
> I have not heard from Joerg since I last replied to his comments to
> Patch 3/3 -- I did my best to explain that there was no issue in the
> single page allocation in pud_free_pmd_page().  From my perspective, the
>  v3 series is good to go.

Well, I admit that this not my area but I agree with Joerg that
allocating memory inside afunction that is supposed to free page table
is far from ideal. More so that the allocation is hardcoded GFP_KERNEL.
We already have this antipattern in functions to allocate page tables
and it has turned to be maintenance PITA longterm. So if there is a way
around that then I would strongly suggest finding a different solution.

Whether that is sufficient to ditch the whole series is not my call
though.
-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2018-06-25 17:53 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-16 23:32 Toshi Kani
2018-05-16 23:32 ` [PATCH v3 1/3] x86/mm: disable ioremap free page handling on x86-PAE Toshi Kani
2018-05-16 23:32 ` [PATCH v3 2/3] ioremap: Update pgtable free interfaces with addr Toshi Kani
2018-05-17  6:47   ` Michal Hocko
2018-05-17 14:32     ` Kani, Toshi
2018-05-16 23:32 ` [PATCH v3 3/3] x86/mm: add TLB purge to free pmd/pte page interfaces Toshi Kani
2018-05-29 14:44   ` Joerg Roedel
2018-05-29 16:10     ` Kani, Toshi
2018-05-30  4:59       ` joro
2018-05-30 15:39         ` Kani, Toshi
2018-06-24 13:19 ` [PATCH v3 0/3] fix free pmd/pte page handlings on x86 Thomas Gleixner
2018-06-25 14:56   ` Kani, Toshi
2018-06-25 17:53     ` Michal Hocko [this message]
2018-06-25 21:15       ` Kani, Toshi
2018-06-26  6:35         ` Michal Hocko
2018-06-26  8:45           ` Thomas Gleixner
2018-06-26  8:54             ` Michal Hocko
2018-06-26 15:25               ` Kani, Toshi

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