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=-9.0 required=3.0 tests=BAYES_00,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 9FB97C48BE5 for ; Thu, 17 Jun 2021 13:37:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7759B610A3 for ; Thu, 17 Jun 2021 13:37:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232837AbhFQNjn (ORCPT ); Thu, 17 Jun 2021 09:39:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:36016 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232844AbhFQNjf (ORCPT ); Thu, 17 Jun 2021 09:39:35 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D3482610A3; Thu, 17 Jun 2021 13:37:27 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1ltsD0-008BeV-0E; Thu, 17 Jun 2021 14:37:26 +0100 Date: Thu, 17 Jun 2021 14:37:25 +0100 Message-ID: <87h7hwd33e.wl-maz@kernel.org> From: Marc Zyngier To: Will Deacon Cc: Yanan Wang , Quentin Perret , Alexandru Elisei , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Catalin Marinas , James Morse , Julien Thierry , Suzuki K Poulose , Gavin Shan , wanghaibin.wang@huawei.com, zhukeqian1@huawei.com, yuzenghui@huawei.com Subject: Re: [PATCH v7 4/4] KVM: arm64: Move guest CMOs to the fault handlers In-Reply-To: <20210617132115.GA24656@willie-the-truck> References: <20210617105824.31752-1-wangyanan55@huawei.com> <20210617105824.31752-5-wangyanan55@huawei.com> <20210617124557.GB24457@willie-the-truck> <87k0msd4ue.wl-maz@kernel.org> <20210617132115.GA24656@willie-the-truck> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: will@kernel.org, wangyanan55@huawei.com, qperret@google.com, alexandru.elisei@arm.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, gshan@redhat.com, wanghaibin.wang@huawei.com, zhukeqian1@huawei.com, yuzenghui@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 17 Jun 2021 14:21:16 +0100, Will Deacon wrote: > > On Thu, Jun 17, 2021 at 01:59:37PM +0100, Marc Zyngier wrote: > > On Thu, 17 Jun 2021 13:45:57 +0100, > > Will Deacon wrote: > > > On Thu, Jun 17, 2021 at 06:58:24PM +0800, Yanan Wang wrote: > > > > @@ -606,6 +618,14 @@ static int stage2_map_walker_try_leaf(u64 addr, u64 end, u32 level, > > > > stage2_put_pte(ptep, data->mmu, addr, level, mm_ops); > > > > } > > > > > > > > + /* Perform CMOs before installation of the guest stage-2 PTE */ > > > > + if (mm_ops->clean_invalidate_dcache && stage2_pte_cacheable(pgt, new)) > > > > + mm_ops->clean_invalidate_dcache(kvm_pte_follow(new, mm_ops), > > > > + granule); > > > > + > > > > + if (mm_ops->invalidate_icache && stage2_pte_executable(new)) > > > > + mm_ops->invalidate_icache(kvm_pte_follow(new, mm_ops), granule); > > > > > > One thing I'm missing here is why we need the indirection via mm_ops. Are > > > there cases where we would want to pass a different function pointer for > > > invalidating the icache? If not, why not just call the function directly? > > > > > > Same for the D side. > > > > If we didn't do that, we'd end-up having to track whether the guest > > context requires CMOs with additional flags, which is pretty ugly (see > > v5 of this series for reference [1]). > > Fair enough, although the function pointers here _are_ being used as > flags, as they only ever have one of two possible values (NULL or > the CMO function), so it's a shame to bring in the indirect branch > as well. What I hope eventually is to get rid of some of the FWB tracking we have for the host in the protected case, and use the same abstraction. > > > It also means that we would have to drag the CM functions into the EL2 > > object, something that we don't need with this approach. > > I think it won't be long before we end up with CMO functions at EL2 and > you'd hope we'd be able to use the same code as EL1 for something like > that. But I also wouldn't want to put money on it... It we reach that stage, I'll be happy to try and move these function into some shared location. > Anyway, no strong opinion on this, it just jumped out when I skimmed the > patches. Thanks, M. -- Without deviation from the norm, progress is not possible.