Messages in this thread | | | Subject | Re: [RFC PATCH V2 0/7] Do not read from descripto ring | From | Jason Wang <> | Date | Thu, 6 May 2021 11:20:30 +0800 |
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在 2021/4/23 下午4:09, Jason Wang 写道: > Hi: > > Sometimes, the driver doesn't trust the device. This is usually > happens for the encrtpyed VM or VDUSE[1]. In both cases, technology > like swiotlb is used to prevent the poking/mangling of memory from the > device. But this is not sufficient since current virtio driver may > trust what is stored in the descriptor table (coherent mapping) for > performing the DMA operations like unmap and bounce so the device may > choose to utilize the behaviour of swiotlb to perform attacks[2]. > > To protect from a malicous device, this series store and use the > descriptor metadata in an auxiliay structure which can not be accessed > via swiotlb instead of the ones in the descriptor table. This means > the descriptor table is write-only from the view of the driver. > > Actually, we've almost achieved that through packed virtqueue and we > just need to fix a corner case of handling mapping errors. For split > virtqueue we just follow what's done in the packed. > > Note that we don't duplicate descriptor medata for indirect > descriptors since it uses stream mapping which is read only so it's > safe if the metadata of non-indirect descriptors are correct. > > For split virtqueue, the change increase the footprint due the the > auxiliary metadata but it's almost neglectlable in the simple test > like pktgen or netpef. > > Slightly tested with packed on/off, iommu on/of, swiotlb force/off in > the guest. > > Please review. > > Changes from V1: > - Always use auxiliary metadata for split virtqueue > - Don't read from descripto when detaching indirect descriptor
Hi Michael:
Our QE see no regression on the perf test for 10G but some regressions (5%-10%) on 40G card.
I think this is expected since we increase the footprint, are you OK with this and we can try to optimize on top or you have other ideas?
Thanks
> > [1] > https://lore.kernel.org/netdev/fab615ce-5e13-a3b3-3715-a4203b4ab010@redhat.com/T/ > [2] > https://yhbt.net/lore/all/c3629a27-3590-1d9f-211b-c0b7be152b32@redhat.com/T/#mc6b6e2343cbeffca68ca7a97e0f473aaa871c95b > > Jason Wang (7): > virtio-ring: maintain next in extra state for packed virtqueue > virtio_ring: rename vring_desc_extra_packed > virtio-ring: factor out desc_extra allocation > virtio_ring: secure handling of mapping errors > virtio_ring: introduce virtqueue_desc_add_split() > virtio: use err label in __vring_new_virtqueue() > virtio-ring: store DMA metadata in desc_extra for split virtqueue > > drivers/virtio/virtio_ring.c | 201 +++++++++++++++++++++++++---------- > 1 file changed, 144 insertions(+), 57 deletions(-) >
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