From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f199.google.com (mail-io0-f199.google.com [209.85.223.199]) by kanga.kvack.org (Postfix) with ESMTP id A11036B026D for ; Wed, 20 Sep 2017 21:37:16 -0400 (EDT) Received: by mail-io0-f199.google.com with SMTP id e9so7515082iod.4 for ; Wed, 20 Sep 2017 18:37:16 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id i90sor111529ioo.331.2017.09.20.18.37.15 for (Google Transport Security); Wed, 20 Sep 2017 18:37:15 -0700 (PDT) Date: Wed, 20 Sep 2017 19:37:12 -0600 From: Tycho Andersen Subject: Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) Message-ID: <20170921013712.lznwkkmdmp64vaiq@docker> References: <20170907173609.22696-1-tycho@docker.com> <20170907173609.22696-4-tycho@docker.com> <34454a32-72c2-c62e-546c-1837e05327e1@intel.com> <20170920223452.vam3egenc533rcta@smitten> <97475308-1f3d-ea91-5647-39231f3b40e5@intel.com> <20170921000901.v7zo4g5edhqqfabm@docker> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com, Marco Benatto , Juerg Haefliger , x86@kernel.org On Wed, Sep 20, 2017 at 05:27:02PM -0700, Dave Hansen wrote: > On 09/20/2017 05:09 PM, Tycho Andersen wrote: > >> I think the only thing that will really help here is if you batch the > >> allocations. For instance, you could make sure that the per-cpu-pageset > >> lists always contain either all kernel or all user data. Then remap the > >> entire list at once and do a single flush after the entire list is consumed. > > Just so I understand, the idea would be that we only flush when the > > type of allocation alternates, so: > > > > kmalloc(..., GFP_KERNEL); > > kmalloc(..., GFP_KERNEL); > > /* remap+flush here */ > > kmalloc(..., GFP_HIGHUSER); > > /* remap+flush here */ > > kmalloc(..., GFP_KERNEL); > > Not really. We keep a free list per migrate type, and a per_cpu_pages > (pcp) list per migratetype: > > > struct per_cpu_pages { > > int count; /* number of pages in the list */ > > int high; /* high watermark, emptying needed */ > > int batch; /* chunk size for buddy add/remove */ > > > > /* Lists of pages, one per migrate type stored on the pcp-lists */ > > struct list_head lists[MIGRATE_PCPTYPES]; > > }; > > The migratetype is derived from the GFP flags in > gfpflags_to_migratetype(). In general, GFP_HIGHUSER and GFP_KERNEL come > from different migratetypes, so they come from different free lists. > > In your case above, the GFP_HIGHUSER allocation come through the > MIGRATE_MOVABLE pcp list while the GFP_KERNEL ones come from the > MIGRATE_UNMOVABLE one. Since we add a bunch of pages to those lists at > once, you could do all the mapping/unmapping/flushing on a bunch of > pages at once > > Or, you could hook your code into the places where the migratetype of > memory is changed (set_pageblock_migratetype(), plus where we fall > back). Those changes are much more rare than page allocation. I see, thanks for all this discussion. It has been very helpful! Tycho -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org