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=-17.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,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 B5047C433DB for ; Mon, 15 Mar 2021 17:03:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87D4964DE0 for ; Mon, 15 Mar 2021 17:03:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234256AbhCORBz (ORCPT ); Mon, 15 Mar 2021 13:01:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:60984 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234806AbhCORBk (ORCPT ); Mon, 15 Mar 2021 13:01:40 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E790E64D9D; Mon, 15 Mar 2021 17:01:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615827699; bh=XZi122AEwWqMj9ZZvX8bMJnPSkj+5a7gkjWIRRfb/CU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PU/i5m3ktp2+u0LV2ng5ubQko8BQTNYwC8oH77rIUeWFethPfizyDHZJ7kg5J9JDH fefW0YFTxENH9St6Yw3CPnDMziw0oHa6O5pDbK9J1e2ska7lWn34WWnMixQzlFtv41 FXhGQYpSEIouonp1bTdKF3BKCCScBXfbKRAE0D5LitzG9zJ2boQH50Yy5i5wPvtyB1 l6gW/DcFs8YgsE/cbGjcc9LSUdOTLXNupoReYd5JPAb8xxWHGkmklvgyFP1I5KxHC7 vbj6mbYmAQ4ljsuEwDzLmoC684rEn85CbNHBxQfX2BqpKyOgi7VeU83c2mW7nwniSs Y13WQwjtm1oLQ== Date: Mon, 15 Mar 2021 17:01:33 +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, seanjc@google.com, mate.toth-pal@arm.com, linux-kernel@vger.kernel.org, robh+dt@kernel.org, linux-arm-kernel@lists.infradead.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, tabba@google.com, ardb@kernel.org, mark.rutland@arm.com, dbrazdil@google.com Subject: Re: [PATCH v5 29/36] KVM: arm64: Use page-table to track page ownership Message-ID: <20210315170133.GH3430@willie-the-truck> References: <20210315143536.214621-1-qperret@google.com> <20210315143536.214621-30-qperret@google.com> <20210315163618.GF3430@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 Mon, Mar 15, 2021 at 04:53:18PM +0000, Quentin Perret wrote: > On Monday 15 Mar 2021 at 16:36:19 (+0000), Will Deacon wrote: > > On Mon, Mar 15, 2021 at 02:35:29PM +0000, Quentin Perret wrote: > > > As the host stage 2 will be identity mapped, all the .hyp memory regions > > > and/or memory pages donated to protected guestis will have to marked > > > invalid in the host stage 2 page-table. At the same time, the hypervisor > > > will need a way to track the ownership of each physical page to ensure > > > memory sharing or donation between entities (host, guests, hypervisor) is > > > legal. > > > > > > In order to enable this tracking at EL2, let's use the host stage 2 > > > page-table itself. The idea is to use the top bits of invalid mappings > > > to store the unique identifier of the page owner. The page-table owner > > > (the host) gets identifier 0 such that, at boot time, it owns the entire > > > IPA space as the pgd starts zeroed. > > > > > > Provide kvm_pgtable_stage2_set_owner() which allows to modify the > > > ownership of pages in the host stage 2. It re-uses most of the map() > > > logic, but ends up creating invalid mappings instead. This impacts > > > how we do refcount as we now need to count invalid mappings when they > > > are used for ownership tracking. > > > > > > Signed-off-by: Quentin Perret > > > --- > > > arch/arm64/include/asm/kvm_pgtable.h | 21 +++++ > > > arch/arm64/kvm/hyp/pgtable.c | 127 ++++++++++++++++++++++----- > > > 2 files changed, 124 insertions(+), 24 deletions(-) > > > > > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > > > index 4ae19247837b..683e96abdc24 100644 > > > --- a/arch/arm64/include/asm/kvm_pgtable.h > > > +++ b/arch/arm64/include/asm/kvm_pgtable.h > > > @@ -238,6 +238,27 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, > > > u64 phys, enum kvm_pgtable_prot prot, > > > void *mc); > > > > > > +/** > > > + * kvm_pgtable_stage2_set_owner() - Annotate invalid mappings with metadata > > > + * encoding the ownership of a page in the > > > + * IPA space. > > > > The function does more than this, though, as it will also go ahead and unmap > > existing valid mappings which I think should be mentioned here, no? > > Right, I see why you mean. How about: > > 'Unmap and annotate pages in the IPA space to track ownership' I think I'd go with: 'Unmap pages and annotate the invalid mappings with ownership metadata for the unmapped IPA range.' as it's the page-table which is annotated, not the actual pages (which could potentially be mapped by other page-tables). Will