From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Morel Subject: Re: [PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature Date: Mon, 6 Jul 2020 17:01:47 +0200 Message-ID: <42f3733d-9f68-91b3-29f9-e88dd4495886@linux.ibm.com> References: <1592390637-17441-1-git-send-email-pmorel@linux.ibm.com> <1592390637-17441-2-git-send-email-pmorel@linux.ibm.com> <20200629115651-mutt-send-email-mst@kernel.org> <20200629180526.41d0732b.cohuck@redhat.com> <26ecd4c6-837b-1ce6-170b-a0155e4dd4d4@linux.ibm.com> <20200706163340.2ce7a5f2.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200706163340.2ce7a5f2.cohuck@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Cornelia Huck Cc: "Michael S. Tsirkin" , linux-kernel@vger.kernel.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, jasowang@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, heiko.carstens@de.ibm.com, gor@linux.ibm.com List-Id: virtualization@lists.linuxfoundation.org On 2020-07-06 16:33, Cornelia Huck wrote: > On Mon, 6 Jul 2020 15:37:37 +0200 > Pierre Morel wrote: > >> On 2020-07-02 15:03, Pierre Morel wrote: >>> >>> >>> On 2020-06-29 18:05, Cornelia Huck wrote: >>>> On Mon, 29 Jun 2020 11:57:14 -0400 >>>> "Michael S. Tsirkin" wrote: >>>> >>>>> On Wed, Jun 17, 2020 at 12:43:57PM +0200, Pierre Morel wrote: >>>>>> An architecture protecting the guest memory against unauthorized host >>>>>> access may want to enforce VIRTIO I/O device protection through the >>>>>> use of VIRTIO_F_IOMMU_PLATFORM. >>>>>> >>>>>> Let's give a chance to the architecture to accept or not devices >>>>>> without VIRTIO_F_IOMMU_PLATFORM. >>>>>> >>>>>> Signed-off-by: Pierre Morel >>>>>> Acked-by: Jason Wang >>>>>> Acked-by: Christian Borntraeger >>>>>> --- >>>>>>   arch/s390/mm/init.c     |  6 ++++++ >>>>>>   drivers/virtio/virtio.c | 22 ++++++++++++++++++++++ >>>>>>   include/linux/virtio.h  |  2 ++ >>>>>>   3 files changed, 30 insertions(+) >>>> >>>>>> @@ -179,6 +194,13 @@ int virtio_finalize_features(struct >>>>>> virtio_device *dev) >>>>>>       if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) >>>>>>           return 0; >>>>>> +    if (arch_needs_virtio_iommu_platform(dev) && >>>>>> +        !virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) { >>>>>> +        dev_warn(&dev->dev, >>>>>> +             "virtio: device must provide VIRTIO_F_IOMMU_PLATFORM\n"); >>>>>> +        return -ENODEV; >>>>>> +    } >>>>>> + >>>>>>       virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK); >>>>>>       status = dev->config->get_status(dev); >>>>>>       if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) { >>>>> >>>>> Well don't you need to check it *before* VIRTIO_F_VERSION_1, not after? >>>> >>>> But it's only available with VERSION_1 anyway, isn't it? So it probably >>>> also needs to fail when this feature is needed if VERSION_1 has not been >>>> negotiated, I think. >> >> >> would be something like: >> >> - if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) >> - return 0; >> + if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) { >> + ret = arch_accept_virtio_features(dev); >> + if (ret) >> + dev_warn(&dev->dev, >> + "virtio: device must provide >> VIRTIO_F_VERSION_1\n"); >> + return ret; >> + } > > That looks wrong; I think we want to validate in all cases. What about: > > ret = arch_accept_virtio_features(dev); // this can include checking for > // older or newer features > if (ret) > // assume that the arch callback moaned already > return ret; > > if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) > return 0; > > // do the virtio-1 only FEATURES_OK dance hum, you are right, I was too focused on keeping my simple arch_accept_virtio_features() function unchanged. It must be more general. > >> >> >> just a thought on the function name: >> It becomes more general than just IOMMU_PLATFORM related. >> >> What do you think of: >> >> arch_accept_virtio_features() > > Or maybe arch_validate_virtio_features()? OK validated. Thanks, Pierre -- Pierre Morel IBM Lab Boeblingen