Messages in this thread | | | Subject | Re: [PATCH] s390: protvirt: virtio: Refuse device without IOMMU | From | Pierre Morel <> | Date | Fri, 12 Jun 2020 11:21:08 +0200 |
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On 2020-06-11 05:10, Jason Wang wrote: > > On 2020/6/10 下午9:11, 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 <pmorel@linux.ibm.com> >> --- >> 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; > > > I wonder whether we need move it to virtio core instead of ccw. > > I think the other memory protection technologies may suffer from this as > well. > > Thanks >
What would you think of the following, also taking into account Connie's comment on where the test should be done:
- declare a weak function in virtio.c code, returning that memory protection is not in use.
- overwrite the function in the arch code
- call this function inside core virtio_finalize_features() and if required fail if the device don't have VIRTIO_F_IOMMU_PLATFORM.
Alternative could be to test a global variable that the architecture would overwrite if needed but I find the weak function solution more flexible.
With a function, we also have the possibility to provide the device as argument and take actions depending it, this may answer Halil's concern.
Regards, Pierre
-- Pierre Morel IBM Lab Boeblingen
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