From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] s390: protvirt: virtio: Refuse device without IOMMU References: <1591794711-5915-1-git-send-email-pmorel@linux.ibm.com> <20200610152431.358fded7.cohuck@redhat.com> <54b28498-a6a7-4be2-9d2c-aef46c7fc642@linux.ibm.com> <20200610165305.1a34c548.cohuck@redhat.com> From: Pierre Morel Message-ID: <8b15139d-cd38-0861-1510-9a53530a4637@linux.ibm.com> Date: Wed, 10 Jun 2020 17:27:01 +0200 MIME-Version: 1.0 In-Reply-To: <20200610165305.1a34c548.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: To: Cornelia Huck Cc: linux-kernel@vger.kernel.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, mst@redhat.com, jasowang@redhat.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org On 2020-06-10 16:53, Cornelia Huck wrote: > On Wed, 10 Jun 2020 16:37:55 +0200 > Pierre Morel wrote: > >> On 2020-06-10 15:24, Cornelia Huck wrote: >>> On Wed, 10 Jun 2020 15:11:51 +0200 >>> Pierre Morel wrote: >>> >>>> Protected Virtualisation protects the memory of the guest and >>>> do not allow a the host to access all of its memory. >>>> >>>> Let's refuse a VIRTIO device which does not use IOMMU >>>> protected access. >>>> >>>> Signed-off-by: Pierre Morel >>>> --- >>>> drivers/s390/virtio/virtio_ccw.c | 5 +++++ >>>> 1 file changed, 5 insertions(+) >>>> >>>> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c >>>> index 5730572b52cd..06ffbc96587a 100644 >>>> --- a/drivers/s390/virtio/virtio_ccw.c >>>> +++ b/drivers/s390/virtio/virtio_ccw.c >>>> @@ -986,6 +986,11 @@ static void virtio_ccw_set_status(struct virtio_device *vdev, u8 status) >>>> if (!ccw) >>>> return; >>>> >>>> + /* Protected Virtualisation guest needs IOMMU */ >>>> + if (is_prot_virt_guest() && >>>> + !__virtio_test_bit(vdev, VIRTIO_F_IOMMU_PLATFORM)) >>>> + status &= ~VIRTIO_CONFIG_S_FEATURES_OK; >>>> + >>> >>> set_status seems like an odd place to look at features; shouldn't that >>> rather be done in finalize_features? >> >> Right, looks better to me too. >> What about: >> >> >> >> diff --git a/drivers/s390/virtio/virtio_ccw.c >> b/drivers/s390/virtio/virtio_ccw.c >> index 06ffbc96587a..227676297ea0 100644 >> --- a/drivers/s390/virtio/virtio_ccw.c >> +++ b/drivers/s390/virtio/virtio_ccw.c >> @@ -833,6 +833,11 @@ static int virtio_ccw_finalize_features(struct >> virtio_device *vdev) >> ret = -ENOMEM; >> goto out_free; >> } >> + >> + if (is_prot_virt_guest() && >> + !__virtio_test_bit(vdev, VIRTIO_F_IOMMU_PLATFORM)) > > Add a comment, and (maybe) a message? > > Otherwise, I think this is fine, as it should fail the probe, which is > what we want. yes right a message is needed. and I extend a little the comment I had before. thanks Regards, Pierre -- Pierre Morel IBM Lab Boeblingen