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X-IronPort-AV: E=McAfee;i="6600,9927,10838"; a="410906318" X-IronPort-AV: E=Sophos;i="6.02,160,1688454000"; d="scan'208";a="410906318" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Sep 2023 08:56:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10838"; a="816486416" X-IronPort-AV: E=Sophos;i="6.02,160,1688454000"; d="scan'208";a="816486416" Received: from rdromms-mobl4.amr.corp.intel.com (HELO [10.212.158.204]) ([10.212.158.204]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Sep 2023 08:56:31 -0700 Message-ID: Date: Tue, 19 Sep 2023 08:56:30 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [RFC PATCH 00/14] Prevent cross-cache attacks in the SLUB allocator Content-Language: en-US To: Matteo Rizzo , Ingo Molnar Cc: "Lameter, Christopher" , penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, corbet@lwn.net, luto@kernel.org, peterz@infradead.org, jannh@google.com, evn@google.com, poprdi@google.com, jordyzomer@google.com, Linus Torvalds References: <20230915105933.495735-1-matteorizzo@google.com> <7a4f5128-28fd-3c5f-34c2-1c34f4448174@intel.com> <1d7573c0-ebbc-6ed2-f152-1045eb0542f9@os.amperecomputing.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 64C8CC000C X-Rspam-User: X-Stat-Signature: b4eeww1dpmiju4fgz66xssj141s8ymgy X-Rspamd-Server: rspam03 X-HE-Tag: 1695138996-26566 X-HE-Meta: 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 KxTkxjLR 4syQByHTvMNYokK6RBeRDPUMMHHNTLEhXtJ3BjyNd96Cduv7or1WLoOLEkSCnJeCTt9kKVInreBL8agim/0gYFUMKLJ938p2TFoOG/CLQxnW0U7mqwZS1d8nbCTnWoU3EYC/ulWB90Ud4KSEtLhkJpGQCwm5upQpyw7Ci3VoPVEWhM7aLbdogpwWCQL28KxrfJckBCHxO8bZCqJ3//CnPBpGlx85A7lIbo4nhHJIx7kpXZxV2R85l65CvMkBXnowKmBehB8Bnf8msIz4= 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 9/19/23 06:42, Matteo Rizzo wrote: > On Mon, 18 Sept 2023 at 19:39, Ingo Molnar wrote: >> What's the split of the increase in overhead due to SLAB_VIRTUAL=y, between >> user-space execution and kernel-space execution? >> > Same benchmark as before (compiling a kernel on a system running the patched > kernel): Thanks for running those. One more situation that comes to mind is how this will act under memory pressure. Will some memory pressure make contention on 'slub_kworker_lock' visible or make the global TLB flushes less bearable? In any case, none of this looks _catastrophic_. It's surely a cost that some folks will pay. But I really do think it needs to be more dynamic. There are a _couple_ of reasons for this. If it's only a compile-time option, it's never going to get turned on except for maybe ChromeOS and the datacenter folks that are paranoid. I suspect the distros will never turn it on. A lot of questions get easier if you can disable/enable it at runtime. For instance, what do you do if the virtual area fills up? You _could_ just go back to handing out direct map addresses. Less secure? Yep. But better than crashing (for some folks). It also opens up the door to do this per-slab. That alone would be a handy debugging option.