From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by lists.ozlabs.org (Postfix) with ESMTP id 3y9q591kX8zDqv8 for ; Tue, 10 Oct 2017 05:48:28 +1100 (AEDT) Date: Mon, 9 Oct 2017 19:48:29 +0100 From: Will Deacon To: Michal Hocko Cc: Pavel Tatashin , Mark Rutland , catalin.marinas@arm.com, linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, kasan-dev@googlegroups.com, borntraeger@de.ibm.com, heiko.carstens@de.ibm.com, davem@davemloft.net, willy@infradead.org, ard.biesheuvel@linaro.org, sam@ravnborg.org, mgorman@techsingularity.net, Steve Sistare , daniel.m.jordan@oracle.com, bob.picco@oracle.com Subject: Re: [PATCH v9 09/12] mm/kasan: kasan specific map populate function Message-ID: <20171009184828.GD30828@arm.com> References: <20170920201714.19817-1-pasha.tatashin@oracle.com> <20170920201714.19817-10-pasha.tatashin@oracle.com> <20171003144845.GD4931@leverpostej> <20171009171337.GE30085@arm.com> <20171009181433.wevxa447d4g6kdsj@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20171009181433.wevxa447d4g6kdsj@dhcp22.suse.cz> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Oct 09, 2017 at 08:14:33PM +0200, Michal Hocko wrote: > On Mon 09-10-17 13:51:47, Pavel Tatashin wrote: > > I can go back to that approach, if Michal OK with it. But, that would > > mean that I would need to touch every single architecture that > > implements vmemmap_populate(), and also pass flags at least through > > these functions on every architectures (some have more than one > > decided by configs).: > > > > vmemmap_populate() > > vmemmap_populate_basepages() > > vmemmap_populate_hugepages() > > vmemmap_pte_populate() > > __vmemmap_alloc_block_buf() > > alloc_block_buf() > > vmemmap_alloc_block() > > > > IMO, while I understand that it looks strange that we must walk page > > table after creating it, it is a better approach: more enclosed as it > > effects kasan only, and more universal as it is in common code. > > While I understand that gfp mask approach might look better at first > sight this is by no means a general purpose API so I would rather be > pragmatic and have a smaller code footprint than a more general > interface. Kasan is pretty much a special case and doing a one time > initialization 2 pass thing is imho acceptable. If this turns out to be > impractical in future then let's fix it up but right now I would rather > go a simpler path. I think the simpler path for arm64 is really to say when we want the memory zeroing as opposed to exposing pmd_large/pud_large macros. Those are likely to grow more users too, but are difficult to use correctly as we have things like contiguous ptes that map to a granule smaller than a pmd. I proposed an alternative solution to Pavel already, but it could be made less general purpose by marking the function __meminit and only having it do anything if KASAN is compiled in. Will