Messages in this thread | | | Date | Wed, 15 Jul 2020 05:50:19 -0400 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH v7 2/2] s390: virtio: PV needs VIRTIO I/O device protection |
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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 <pmorel@linux.ibm.com> > Reviewed-by: Cornelia Huck <cohuck@redhat.com> > Acked-by: Halil Pasic <pasic@linux.ibm.com> > Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> > --- > 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 <asm/kasan.h> > #include <asm/dma-mapping.h> > #include <asm/uv.h> > +#include <linux/virtio_config.h> > > 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.
I'm not sure what to do with this yet, will try to think about it over the weekend. Thanks!
> -- > 2.25.1
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