From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 061CAC54E5D for ; Mon, 18 Mar 2024 15:20:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 738E16B0088; Mon, 18 Mar 2024 11:20:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6C1F36B0089; Mon, 18 Mar 2024 11:20:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 562CA6B008C; Mon, 18 Mar 2024 11:20:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 3FB7A6B0088 for ; Mon, 18 Mar 2024 11:20:02 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id D5C341407B7 for ; Mon, 18 Mar 2024 15:20:01 +0000 (UTC) X-FDA: 81910520202.30.9295B0D Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf16.hostedemail.com (Postfix) with ESMTP id 90E0718001C for ; Mon, 18 Mar 2024 15:19:58 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=GCTFw8mP; spf=none (imf16.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1710775199; a=rsa-sha256; cv=none; b=fTUUUjOBe9vsyfl1tJBzqNxOvYsIr8+V5B1fNEC7SCdmwoWlNGXSfqtCVXpkKZ29tLnK3o lFbrXZZOworZkFHCIVNDWFK5jsbkQs9IbO26qfIvcCOySzU68ewjmHB3p3nCWWI0EPKOx6 Y+SukJMJXGm4DrsOiLQq/E4Xpt2oRWg= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=GCTFw8mP; spf=none (imf16.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1710775199; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=rayCM2prt2//9KKvtSxS+IFFDRjg7qyBPxuMRQQtlQg=; b=R9IVMUkbBnrE0Oy2h8emNPH6DatwExW11lqJ0gdQKbraEuJuzQhFOooqhuQ2akIRVaLvtT ta+cAHrMjmXpXmR5nk4yNN03qlOy94B24vLsguJ7C9ELjP+JB80NyqS45VnKYMPSeo9F3I 8Yv61Ilt5UnxjtdIVfT4VKZZe21Q9Kc= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rayCM2prt2//9KKvtSxS+IFFDRjg7qyBPxuMRQQtlQg=; b=GCTFw8mPDwozA5wqrfuTAhT5Oz Ruhi2mLN6L8F4/1OiORKj4bu5CoFp8GQ6y/4nvZK2VeGi5aBS1FfGMcVan4ia5IxP0xsiz31nabSv PHtpbVNvKBK3DR29b+8dhwxA/8J9hGSchtqopAfa7Pzz0FRollz3Br0VPHqudDXvyHPelWr203Kxb lxabtQS26yYMqUsANvtP/91eTCxMLDLTp4W6+UANLwoxX0IAQpQ9i4f0YDFWVGYoncx72SoJzrs/E qm+tFyxkWkZDNsZSvO+AgRJUjrm6RQo+0qBR3NGguVAh2V0SG4d2DljCNf/KoGYWMmj2m/T6gyMiY t0uS0nbw==; Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rmEmE-0000000HPue-3X4m; Mon, 18 Mar 2024 15:19:50 +0000 Date: Mon, 18 Mar 2024 15:19:50 +0000 From: Matthew Wilcox To: Pasha Tatashin Cc: David Laight , "H. Peter Anvin" , Kent Overstreet , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "x86@kernel.org" , "bp@alien8.de" , "brauner@kernel.org" , "bristot@redhat.com" , "bsegall@google.com" , "dave.hansen@linux.intel.com" , "dianders@chromium.org" , "dietmar.eggemann@arm.com" , "eric.devolder@oracle.com" , "hca@linux.ibm.com" , "hch@infradead.org" , "jacob.jun.pan@linux.intel.com" , "jgg@ziepe.ca" , "jpoimboe@kernel.org" , "jroedel@suse.de" , "juri.lelli@redhat.com" , "kinseyho@google.com" , "kirill.shutemov@linux.intel.com" , "lstoakes@gmail.com" , "luto@kernel.org" , "mgorman@suse.de" , "mic@digikod.net" , "michael.christie@oracle.com" , "mingo@redhat.com" , "mjguzik@gmail.com" , "mst@redhat.com" , "npiggin@gmail.com" , "peterz@infradead.org" , "pmladek@suse.com" , "rick.p.edgecombe@intel.com" , "rostedt@goodmis.org" , "surenb@google.com" , "tglx@linutronix.de" , "urezki@gmail.com" , "vincent.guittot@linaro.org" , "vschneid@redhat.com" Subject: Re: [RFC 00/14] Dynamic Kernel Stacks Message-ID: References: <20240311164638.2015063-1-pasha.tatashin@soleen.com> <2cb8f02d-f21e-45d2-afe2-d1c6225240f3@zytor.com> <2qp4uegb4kqkryihqyo6v3fzoc2nysuhltc535kxnh6ozpo5ni@isilzw7nth42> <39F17EC4-7844-4111-BF7D-FFC97B05D9FA@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 90E0718001C X-Stat-Signature: ppqn1nt15hrcc3wjj5ktgrermgpk4ktg X-Rspam-User: X-HE-Tag: 1710775198-625280 X-HE-Meta: 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 U+F/QgHo C/bLLdUBaVH6pPJHlRurOYhAXgWiTF+Krlb7/xwEu7SuUisx5KmrVf/Dhq0VqzZ893oSdPZw8t78dch4XtE+xJm0H6r4Nx9cyW0QnAGSTbeUVzbHwzlVTRpGCHxWoO5DYxAcKOy1eP3c3f7UK1PJmilLAeGu99yqSU2Qjl2RfNgteXigKar/kJ+jcD5TrmnRNIbcrBJ7BYDI4FWY= 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: List-Subscribe: List-Unsubscribe: On Mon, Mar 18, 2024 at 11:09:47AM -0400, Pasha Tatashin wrote: > The TLB load is going to be exactly the same as today, we already use > small pages for VMA mapped stacks. We won't need to have extra > flushing either, the mappings are in the kernel space, and once pages > are removed from the page table, no one is going to access that VA > space until that thread enters the kernel again. We will need to > invalidate the VA range only when the pages are mapped, and only on > the local cpu. No; we can pass pointers to our kernel stack to other threads. The obvious one is a mutex; we put a mutex_waiter on our own stack and add its list_head to the mutex's waiter list. I'm sure you can think of many other places we do this (eg wait queues, poll(), select(), etc).