linux/drivers/virtio
Michael S. Tsirkin 0d5415b489 Revert "vring: Force use of DMA API for ARM-based systems with legacy devices"
This reverts commit c7070619f3.

This has been shown to regress on some ARM systems:

by forcing on DMA API usage for ARM systems, we have inadvertently
kicked open a hornets' nest in terms of cache-coherency. Namely that
unless the virtio device is explicitly described as capable of coherent
DMA by firmware, the DMA APIs on ARM and other DT-based platforms will
assume it is non-coherent. This turns out to cause a big problem for the
likes of QEMU and kvmtool, which generate virtio-mmio devices in their
guest DTs but neglect to add the often-overlooked "dma-coherent"
property; as a result, we end up with the guest making non-cacheable
accesses to the vring, the host doing so cacheably, both talking past
each other and things going horribly wrong.

We are working on a safer work-around.

Fixes: c7070619f3 ("vring: Force use of DMA API for ARM-based systems with legacy devices")
Reported-by: Robin Murphy <robin.murphy@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
2017-02-03 23:38:50 +02:00
..
Kconfig docs: fix locations of several documents that got moved 2016-10-24 08:12:35 -02:00
Makefile Add virtio-input driver. 2015-03-29 12:13:52 +10:30
virtio.c virtio: fix memory leak of virtio ida cache layers 2015-12-07 17:28:01 +02:00
virtio_balloon.c virtio: update balloon size in balloon "probe" 2016-10-31 00:21:41 +02:00
virtio_input.c virtio: make find_vqs() checkpatch.pl-friendly 2016-01-12 20:47:06 +02:00
virtio_mmio.c virtio_mmio: Set DMA masks appropriately 2017-01-25 00:33:10 +02:00
virtio_pci_common.c virtio_pci: split vp_try_to_find_vqs into INTx and MSI-X variants 2016-12-16 00:12:49 +02:00
virtio_pci_common.h virtio_pci: use pci_alloc_irq_vectors 2016-12-16 00:12:47 +02:00
virtio_pci_legacy.c virtio_pci: Limit DMA mask to 44 bits for legacy virtio devices 2016-10-31 00:21:39 +02:00
virtio_pci_modern.c virtio_pci_modern: fix complaint by sparse 2016-12-15 06:39:46 +02:00
virtio_ring.c Revert "vring: Force use of DMA API for ARM-based systems with legacy devices" 2017-02-03 23:38:50 +02:00