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28 Apr 2020 17:42:21 -0700 IronPort-SDR: zhoWtPceY9D9x0OnO/3jWidzr31luRzPPhtTBEfwvD/0lLFP8Sfi2HbUCfEgdrZacJ+A17FosR PajfKfUCGQww== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,328,1583222400"; d="scan'208";a="261271330" Received: from meis-mobl1.amr.corp.intel.com (HELO [10.255.231.186]) ([10.255.231.186]) by orsmga006.jf.intel.com with ESMTP; 28 Apr 2020 17:42:20 -0700 Subject: Re: [PATCH v4 2/2] mm/gup/writeback: add callbacks for inaccessible pages To: Claudio Imbrenda Cc: Peter Zijlstra , Andy Lutomirski , linux-next@vger.kernel.org, akpm@linux-foundation.org, jack@suse.cz, kirill@shutemov.name, "Edgecombe, Rick P" , Sean Christopherson , borntraeger@de.ibm.com, david@redhat.com, aarcange@redhat.com, linux-mm@kvack.org, frankja@linux.ibm.com, sfr@canb.auug.org.au, jhubbard@nvidia.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Will Deacon , "Williams, Dan J" , pasic@linux.ibm.com References: <20200306132537.783769-1-imbrenda@linux.ibm.com> <20200306132537.783769-3-imbrenda@linux.ibm.com> <3ae46945-0c7b-03cd-700a-a6fe8003c6ab@intel.com> <20200415221754.GM2483@worktop.programming.kicks-ass.net> <20200416141547.29be5ea0@p-imbrenda> <20200416165900.68bd4dba@p-imbrenda> <20200416183431.7216e1d1@p-imbrenda> <396a4ece-ec66-d023-2c7e-f09f84b358bc@intel.com> <42fccd01-7e16-b18f-cd81-4040857d80d4@intel.com> <20200429013955.2b59bd99@p-imbrenda> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200429013955.2b59bd99@p-imbrenda> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/28/20 4:39 PM, Claudio Imbrenda wrote: >> From where I'm standing, we have a hook in the core VM that can't >> possibly work with some existing kernel functionality and has >> virtually no chance of getting used on a second architecture. > it seems to work at least for us, so it does possibly work :) I think all you're saying is that it's been very lightly tested. :) > regarding second architectures: when we started sending these patches > around, there has been interest from some other architectures, so > just because nobody else needs them now, it doesn't mean nobody will > use them ever. I was really interested in using them... until I looked at them. Conceptually, they do something really useful, but the _implementation_ falls short of its promises. I can't imagine ever using these hooks on x86.