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Tue, 20 Jul 2021 03:38:21 -0700 (PDT) Received: from google.com ([2a00:79e0:d:210:83e0:11ac:c870:2b97]) by smtp.gmail.com with ESMTPSA id a10sm22857100wrm.12.2021.07.20.03.38.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jul 2021 03:38:20 -0700 (PDT) Date: Tue, 20 Jul 2021 11:38:17 +0100 From: Quentin Perret To: Marc Zyngier Subject: Re: [PATCH 03/16] KVM: arm64: Turn kvm_pgtable_stage2_set_owner into kvm_pgtable_stage2_annotate Message-ID: References: <20210715163159.1480168-1-maz@kernel.org> <20210715163159.1480168-4-maz@kernel.org> <871r7t9tgi.wl-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <871r7t9tgi.wl-maz@kernel.org> Cc: kernel-team@android.com, kvm@vger.kernel.org, Srivatsa Vaddagiri , linux-kernel@vger.kernel.org, Shanker R Donthineni , will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Tuesday 20 Jul 2021 at 11:21:17 (+0100), Marc Zyngier wrote: > On Tue, 20 Jul 2021 11:09:21 +0100, > Quentin Perret wrote: > > > > On Thursday 15 Jul 2021 at 17:31:46 (+0100), Marc Zyngier wrote: > > > @@ -815,7 +807,7 @@ int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size, > > > .arg = &map_data, > > > }; > > > > > > - if (owner_id > KVM_MAX_OWNER_ID) > > > + if (!annotation || (annotation & PTE_VALID)) > > > return -EINVAL; > > > > Why do you consider annotation==0 invalid? The assumption so far has > > been that the owner_id for the host is 0, so annotating a range with 0s > > should be a valid operation -- this will be required when e.g. > > transferring ownership of a page back to the host. > > How do you then distinguish it from an empty entry that doesn't map to > anything at all? You don't, but that's beauty of it :) The host starts with a PGD full of zeroes, which in terms of ownership means that it owns the entire (I)PA space. And it loses ownership of a page only when we explicitly annotate it with an owner id != 0. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm