From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH v7 2/2] s390: virtio: PV needs VIRTIO I/O device protection Date: Thu, 16 Jul 2020 13:19:55 +0200 Message-ID: <3782338a-6491-dc35-7c66-97b91a20df0d@de.ibm.com> References: <1594801869-13365-1-git-send-email-pmorel@linux.ibm.com> <1594801869-13365-3-git-send-email-pmorel@linux.ibm.com> <20200715054807-mutt-send-email-mst@kernel.org> <20200715074917-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200715074917-mutt-send-email-mst@kernel.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: "Michael S. Tsirkin" , Jason Wang Cc: Pierre Morel , linux-kernel@vger.kernel.org, pasic@linux.ibm.com, frankja@linux.ibm.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 List-Id: virtualization@lists.linuxfoundation.org On 15.07.20 13:51, Michael S. Tsirkin wrote: > On Wed, Jul 15, 2020 at 06:16:59PM +0800, Jason Wang wrote: >> >> On 2020/7/15 下午5:50, Michael S. Tsirkin wrote: >>> 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. >> If you prefer that, we can simply create an arch/s390/kernel/virtio.c ?