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Tue, 20 Jul 2021 03:38:20 -0700 (PDT) Date: Tue, 20 Jul 2021 11:38:17 +0100 From: Quentin Perret To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, will@kernel.org, dbrazdil@google.com, Srivatsa Vaddagiri , Shanker R Donthineni , James Morse , Suzuki K Poulose , Alexandru Elisei , kernel-team@android.com 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> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210720_033823_399764_C434DF82 X-CRM114-Status: GOOD ( 16.70 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel