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 X-Spam-Level: X-Spam-Status: No, score=-7.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41D5BC433E0 for ; Thu, 4 Feb 2021 17:51:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07A3664E16 for ; Thu, 4 Feb 2021 17:51:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238669AbhBDRvI (ORCPT ); Thu, 4 Feb 2021 12:51:08 -0500 Received: from mail.kernel.org ([198.145.29.99]:36688 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237500AbhBDRtm (ORCPT ); Thu, 4 Feb 2021 12:49:42 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 639A164F41; Thu, 4 Feb 2021 17:48:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612460936; bh=BE4sTc2vQLpAqcnSed7nO8BgiaDvc3jDuHi/BhMHhuw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BJdPmR0qx04Q0OC8F92po0hMHhrRiWvCaxDONmHEOoUlPgCayFyD25VcKG9WAE5Ab dsuh0qli7OfmSqeEkwH0tHklTV6xlGGaJICNA3Bf4Kc2zQEzKSlwDMjJP4OtHhT/Az unbkjzC/50L2YixQX7un0SEMXdb+1hbaD3m5rjR8iUXk/Rs81QPavwoAn0+TmUUQgq c51he+0ZCZ/l4W+Onfm4pbnVfVAQCatI6xGIqlmqFEpLCjf0/tx9tOt5qOom6lDmNU wSXrZoHUHqE8XQVhWEcCQKWNWBHNhIaLyoHPM4WHK/OO4PWoWHpW1XZpP+9r6IK6Aq jy0+RUjalzziw== Date: Thu, 4 Feb 2021 17:48:49 +0000 From: Will Deacon To: Quentin Perret Cc: Catalin Marinas , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Rob Herring , Frank Rowand , devicetree@vger.kernel.org, android-kvm@google.com, linux-kernel@vger.kernel.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Fuad Tabba , Mark Rutland , David Brazdil Subject: Re: [RFC PATCH v2 12/26] KVM: arm64: Introduce a Hyp buddy page allocator Message-ID: <20210204174849.GA21303@willie-the-truck> References: <20210108121524.656872-1-qperret@google.com> <20210108121524.656872-13-qperret@google.com> <20210202181307.GA17311@willie-the-truck> <20210204143106.GA20792@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 04, 2021 at 02:52:52PM +0000, Quentin Perret wrote: > On Thursday 04 Feb 2021 at 14:31:08 (+0000), Will Deacon wrote: > > On Wed, Feb 03, 2021 at 06:33:30PM +0000, Quentin Perret wrote: > > > On Tuesday 02 Feb 2021 at 18:13:08 (+0000), Will Deacon wrote: > > > > On Fri, Jan 08, 2021 at 12:15:10PM +0000, Quentin Perret wrote: > > > > > + * __find_buddy(pool, page 0, order 0) => page 1 > > > > > + * __find_buddy(pool, page 0, order 1) => page 2 > > > > > + * __find_buddy(pool, page 1, order 0) => page 0 > > > > > + * __find_buddy(pool, page 2, order 0) => page 3 > > > > > + */ > > > > > +static struct hyp_page *__find_buddy(struct hyp_pool *pool, struct hyp_page *p, > > > > > + unsigned int order) > > > > > +{ > > > > > + phys_addr_t addr = hyp_page_to_phys(p); > > > > > + > > > > > + addr ^= (PAGE_SIZE << order); > > > > > + if (addr < pool->range_start || addr >= pool->range_end) > > > > > + return NULL; > > > > > > > > Are these range checks only needed because the pool isn't required to be > > > > an exact power-of-2 pages in size? If so, maybe it would be more > > > > straightforward to limit the max order on a per-pool basis depending upon > > > > its size? > > > > > > More importantly, it is because pages outside of the pool are not > > > guaranteed to be covered by the hyp_vmemmap, so I really need to make > > > sure I don't dereference them. > > > > Wouldn't having a per-pool max order help with that? > > The issue is, I have no alignment guarantees for the pools, so I may end > up with max_order = 0 ... Yeah, so you would still need the range tracking, but it would at least help to reduce HYP_MAX_ORDER failed searches each time. Still, we can always do that later. Will