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=-15.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 F0C9BC4338F for ; Fri, 23 Jul 2021 15:55:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D505760E0C for ; Fri, 23 Jul 2021 15:55:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235751AbhGWPOY (ORCPT ); Fri, 23 Jul 2021 11:14:24 -0400 Received: from foss.arm.com ([217.140.110.172]:48256 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235740AbhGWPOC (ORCPT ); Fri, 23 Jul 2021 11:14:02 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E4B5613A1; Fri, 23 Jul 2021 08:54:35 -0700 (PDT) Received: from [192.168.0.110] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D1C443F73D; Fri, 23 Jul 2021 08:54:33 -0700 (PDT) From: Alexandru Elisei Subject: Re: [PATCH 2/5] KVM: arm64: Avoid mapping size adjustment on permission fault To: Marc Zyngier , linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-mm@kvack.org Cc: Sean Christopherson , Matthew Wilcox , Paolo Bonzini , Will Deacon , Quentin Perret , James Morse , Suzuki K Poulose , kernel-team@android.com References: <20210717095541.1486210-1-maz@kernel.org> <20210717095541.1486210-3-maz@kernel.org> Message-ID: Date: Fri, 23 Jul 2021 16:55:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210717095541.1486210-3-maz@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Marc, On 7/17/21 10:55 AM, Marc Zyngier wrote: > Since we only support PMD-sized mappings for THP, getting > a permission fault on a level that results in a mapping > being larger than PAGE_SIZE is a sure indication that we have > already upgraded our mapping to a PMD. > > In this case, there is no need to try and parse userspace page > tables, as the fault information already tells us everything. > > Signed-off-by: Marc Zyngier > --- > arch/arm64/kvm/mmu.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index db6314b93e99..c036a480ca27 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1088,9 +1088,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > * If we are not forced to use page mapping, check if we are > * backed by a THP and thus use block mapping if possible. > */ > - if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) > - vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva, > - &pfn, &fault_ipa); > + if (vma_pagesize == PAGE_SIZE && !force_pte) { Looks like now it's possible to call transparent_hugepage_adjust() for devices (if fault_status != FSC_PERM). Commit 2aa53d68cee6 ("KVM: arm64: Try stage2 block mapping for host device MMIO") makes a good case for the !device check. Was the check removed unintentionally? > + if (fault_status == FSC_PERM && fault_granule > PAGE_SIZE) > + vma_pagesize = fault_granule; > + else > + vma_pagesize = transparent_hugepage_adjust(kvm, memslot, > + hva, &pfn, > + &fault_ipa); > + } This change makes sense to me - we can only get stage 2 permission faults on a leaf entry since stage 2 tables don't have the APTable/XNTable/PXNTable bits. The biggest block mapping size that we support at stage 2 is PMD size (from transparent_hugepage_adjust()), therefore if fault_granule is larger than PAGE_SIZE, then it must be PMD_SIZE. Thanks, Alex > > if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) { > /* Check the VMM hasn't introduced a new VM_SHARED VMA */