Re: [PATCH] s390: protvirt: virtio: Refuse device without IOMMU
From: Mauricio Tavares <hidden>
Date: 2020-06-12 13:45:57
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kvm, linux-s390, lkml
On Wed, Jun 10, 2020 at 12:32 PM Pierre Morel [off-list ref] 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.
Stupid questions: 1. Do all CPU families we care about (which are?) support IOMMU? Ex: would it recognize an ARM thingie with SMMU? [1] 2. Would it make sense to have some kind of yes-I-know-the-consequences-but-I-need-to-have-a-virtio-device-without-iommu-in-this-guest flag?
quoted hunk ↗ jump to hunk
Signed-off-by: Pierre Morel <redacted> --- 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; + /* Write the status to the host. */ vcdev->dma_area->status = status; ccw->cmd_code = CCW_CMD_WRITE_STATUS; --2.25.1
[1] https://developer.arm.com/architectures/system-architectures/system-components/system-mmu-support