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[79.180.10.140]) by smtp.gmail.com with ESMTPSA id 14sm2563305wmk.19.2020.07.15.02.50.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jul 2020 02:50:22 -0700 (PDT) Date: Wed, 15 Jul 2020 05:50:19 -0400 From: "Michael S. Tsirkin" To: Pierre Morel Cc: linux-kernel@vger.kernel.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, jasowang@redhat.com, cohuck@redhat.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, thomas.lendacky@amd.com, david@gibson.dropbear.id.au, linuxram@us.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com Subject: Re: [PATCH v7 2/2] s390: virtio: PV needs VIRTIO I/O device protection Message-ID: <20200715054807-mutt-send-email-mst@kernel.org> References: <1594801869-13365-1-git-send-email-pmorel@linux.ibm.com> <1594801869-13365-3-git-send-email-pmorel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1594801869-13365-3-git-send-email-pmorel@linux.ibm.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Jul 15, 2020 at 10:31:09AM +0200, Pierre Morel wrote: > If protected virtualization is active on s390, the virtio queues are > not accessible to the host, unless VIRTIO_F_IOMMU_PLATFORM has been > negotiated. Use the new arch_validate_virtio_features() interface to > fail probe if that's not the case, preventing a host error on access > attempt. > > Signed-off-by: Pierre Morel > Reviewed-by: Cornelia Huck > Acked-by: Halil Pasic > Acked-by: Christian Borntraeger > --- > arch/s390/mm/init.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c > index 6dc7c3b60ef6..d39af6554d4f 100644 > --- a/arch/s390/mm/init.c > +++ b/arch/s390/mm/init.c > @@ -45,6 +45,7 @@ > #include > #include > #include > +#include > > pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir); > > @@ -161,6 +162,33 @@ bool force_dma_unencrypted(struct device *dev) > return is_prot_virt_guest(); > } > > +/* > + * arch_validate_virtio_features > + * @dev: the VIRTIO device being added > + * > + * Return an error if required features are missing on a guest running > + * with protected virtualization. > + */ > +int arch_validate_virtio_features(struct virtio_device *dev) > +{ > + if (!is_prot_virt_guest()) > + return 0; > + > + if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) { > + dev_warn(&dev->dev, > + "legacy virtio not supported with protected virtualization\n"); > + return -ENODEV; > + } > + > + if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) { > + dev_warn(&dev->dev, > + "support for limited memory access required for protected virtualization\n"); > + return -ENODEV; > + } > + > + return 0; > +} > + > /* protected virtualization */ > static void pv_init(void) > { What bothers me here is that arch code depends on virtio now. It works even with a modular virtio when functions are inline, but it seems fragile: e.g. it breaks virtio as an out of tree module, since layout of struct virtio_device can change. I'm not sure what to do with this yet, will try to think about it over the weekend. Thanks! > -- > 2.25.1