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[216.228.121.65]) by mx.google.com with ESMTPS id l13si61128pgp.571.2019.03.28.13.33.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Mar 2019 13:33:44 -0700 (PDT) Received-SPF: pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.65 as permitted sender) client-ip=216.228.121.65; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=rVH+m+xL; spf=pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.65 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate16.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 28 Mar 2019 13:33:41 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 28 Mar 2019 13:33:43 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 28 Mar 2019 13:33:43 -0700 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 28 Mar 2019 20:33:43 +0000 Subject: Re: [PATCH v2 01/11] mm/hmm: select mmu notifier when selecting HMM To: , CC: , Ralph Campbell , Andrew Morton , Dan Williams References: <20190325144011.10560-1-jglisse@redhat.com> <20190325144011.10560-2-jglisse@redhat.com> From: John Hubbard X-Nvconfidentiality: public Message-ID: Date: Thu, 28 Mar 2019 13:33:42 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <20190325144011.10560-2-jglisse@redhat.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL108.nvidia.com (172.18.146.13) To HQMAIL101.nvidia.com (172.20.187.10) Content-Type: text/plain; charset="utf-8" Content-Language: en-US-large Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1553805221; bh=o+a/SAiZ8f2SWEWLbL14a/AHxKB3R3uRQE9ibApvFzo=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=rVH+m+xL2BxNvS6qdiawWzdzngrp29z3aMootYghbquzyuTBuiD0uULk7EcEdiSxC AgPVAWB3MSZxyWqYw/gZuFZrraF7vPcNztWTNwyqRm2NC1H8XVs+OYVhlgIj1sLUO0 pAbOqrC0xQOMtYZ0srtx3N1GYtooxq6lsFekMrXYmh/rcBNNJgVTG8W5qhnQtZ+DSE q+9//0amEirw0w69sh2gmn1qMlahnuCScS28MQNd1DSfAeM0GDe4asvNuU3lzzs5Mq PZWb5QgvI6PgWgrQVvBA3AF0dxhscVxvV5r0svpUA5+xM8ElkZjty0CNabpUUOSXL+ IsSeRPIxnErHg== 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 3/25/19 7:40 AM, jglisse@redhat.com wrote: > From: J=C3=A9r=C3=B4me Glisse >=20 > To avoid random config build issue, select mmu notifier when HMM is > selected. In any cases when HMM get selected it will be by users that > will also wants the mmu notifier. >=20 > Signed-off-by: J=C3=A9r=C3=B4me Glisse > Acked-by: Balbir Singh > Cc: Ralph Campbell > Cc: Andrew Morton > Cc: John Hubbard > Cc: Dan Williams > --- > mm/Kconfig | 1 + > 1 file changed, 1 insertion(+) >=20 > diff --git a/mm/Kconfig b/mm/Kconfig > index 25c71eb8a7db..0d2944278d80 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -694,6 +694,7 @@ config DEV_PAGEMAP_OPS > =20 > config HMM > bool > + select MMU_NOTIFIER > select MIGRATE_VMA_HELPER > =20 > config HMM_MIRROR >=20 Yes, this is a good move, given that MMU notifiers are completely, indispensably part of the HMM design and implementation. The alternative would also work, but it's not quite as good. I'm listing it in order to forestall any debate:=20 config HMM bool + depends on MMU_NOTIFIER select MIGRATE_VMA_HELPER ...and "depends on" versus "select" is always a subtle question. But in this case, I'd say that if someone wants HMM, there's no advantage in making them know that they must first ensure MMU_NOTIFIER is enabled. After poking around a bit I don't see any obvious downsides either. However, given that you're making this change, in order to avoid odd redundancy, you should also do this: diff --git a/mm/Kconfig b/mm/Kconfig index 0d2944278d80..2e6d24d783f7 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -700,7 +700,6 @@ config HMM config HMM_MIRROR bool "HMM mirror CPU page table into a device page table" depends on ARCH_HAS_HMM - select MMU_NOTIFIER select HMM help Select HMM_MIRROR if you want to mirror range of the CPU page tab= le of a thanks, --=20 John Hubbard NVIDIA