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=-12.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 765A5C433E0 for ; Fri, 12 Mar 2021 09:41:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 349E264FA8 for ; Fri, 12 Mar 2021 09:41:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232905AbhCLJkf (ORCPT ); Fri, 12 Mar 2021 04:40:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:49842 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232397AbhCLJkR (ORCPT ); Fri, 12 Mar 2021 04:40:17 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3961E64FDD; Fri, 12 Mar 2021 09:40:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615542017; bh=IhMRNUcJYwCkDReHSF76lISid/6+vJxJRq5TrqpWgk8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FttZZGnGm4GqH4u+TmUc57P5wbD6izysvvsuuknHB0t9tFFQ2cQUyxJP/LmMkMDPj pBaaPhflRrPTYmpAiwT0ngHHanDpHmZPoRs7X+JJnQ9lmsdsaUrapQE8/wHB66L3Hu aVesI5HypLmSPbqdaaWqDr25iEvI5DhjopJJ0hEA3yEeNosk9xaawcrEhTcWRKRiSJ byZmtWoB7mUSOf5wgOLjHY3cp9Q9veMVqbG3NIvjswUAA8acTGGr0x/S3V/DniQx4j 0+d4EafNVWpjsvT9E+2S9Uv0D5JTLHwiVdzh+eQOaEL5QjPeEq0Xn9UUd3EPKbRAWz EWOc5VUiGsXxg== Date: Fri, 12 Mar 2021 09:40:09 +0000 From: Will Deacon To: Quentin Perret Cc: catalin.marinas@arm.com, maz@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, android-kvm@google.com, linux-kernel@vger.kernel.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, tabba@google.com, mark.rutland@arm.com, dbrazdil@google.com, mate.toth-pal@arm.com, seanjc@google.com, robh+dt@kernel.org, ardb@kernel.org Subject: Re: [PATCH v4 30/34] KVM: arm64: Add kvm_pgtable_stage2_find_range() Message-ID: <20210312094009.GC32016@willie-the-truck> References: <20210310175751.3320106-1-qperret@google.com> <20210310175751.3320106-31-qperret@google.com> <20210311190406.GB31586@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 Fri, Mar 12, 2021 at 05:32:13AM +0000, Quentin Perret wrote: > On Thursday 11 Mar 2021 at 19:04:07 (+0000), Will Deacon wrote: > > On Wed, Mar 10, 2021 at 05:57:47PM +0000, Quentin Perret wrote: > > > + for (level = pgt->start_level; level < KVM_PGTABLE_MAX_LEVELS; level++) { > > > + granule = kvm_granule_size(level); > > > + start = ALIGN_DOWN(addr, granule); > > > + end = start + granule; > > > + > > > + if (!kvm_level_support_block_mappings(level)) > > > + continue; > > > + > > > + if (start < range->start || range->end < end) > > > + continue; > > > + > > > + /* > > > + * Check the presence of existing mappings with incompatible > > > + * permissions within the current block range, and try one level > > > + * deeper if one is found. > > > + */ > > > + ret = kvm_pgtable_walk(pgt, start, granule, &check_perm_walker); > > > + if (ret != -EEXIST) > > > + break; > > > + } > > > > Can you write this as a: > > > > do { > > ... > > } while (level < KVM_PGTABLE_MAX_LEVELS && ret == -EEXIST); > > > > loop? > > I tried it but found it a little less pretty -- the pre-assignment of > level and the increment at the end make it really feel like a for loop > to me: > > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -1098,26 +1098,23 @@ int kvm_pgtable_stage2_find_range(struct kvm_pgtable *pgt, u64 addr, > return ret; > attr &= KVM_PTE_LEAF_S2_COMPAT_MASK; > > - for (level = pgt->start_level; level < KVM_PGTABLE_MAX_LEVELS; level++) { > + ret = -EEXIST; > + level = pgt->start_level; > + do { > granule = kvm_granule_size(level); > start = ALIGN_DOWN(addr, granule); > end = start + granule; > > - if (!kvm_level_support_block_mappings(level)) > - continue; > - > - if (start < range->start || range->end < end) > - continue; Urgh, yes, sorry, I hadn't appreciated what a mess it causes for these guys. Stick with the 'for' loop. Will