From: Halil Pasic pasic@linux.ibm.com
[ Upstream commit 05668e1d74b84c53fbe0f28565e4c9502a6b8a67 ]
Commit 37db8985b211 ("s390/cio: add basic protected virtualization support") breaks virtio-ccw devices with VIRTIO_F_IOMMU_PLATFORM for non Protected Virtualization (PV) guests. The problem is that the dma_mask of the ccw device, which is used by virtio core, gets changed from 64 to 31 bit, because some of the DMA allocations do require 31 bit addressable memory. For PV the only drawback is that some of the virtio structures must end up in ZONE_DMA because we have the bounce the buffers mapped via DMA API anyway.
But for non PV guests we have a problem: because of the 31 bit mask guests bigger than 2G are likely to try bouncing buffers. The swiotlb however is only initialized for PV guests, because we don't want to bounce anything for non PV guests. The first such map kills the guest.
Since the DMA API won't allow us to specify for each allocation whether we need memory from ZONE_DMA (31 bit addressable) or any DMA capable memory will do, let us use coherent_dma_mask (which is used for allocations) to force allocating form ZONE_DMA while changing dma_mask to DMA_BIT_MASK(64) so that at least the streaming API will regard the whole memory DMA capable.
Signed-off-by: Halil Pasic pasic@linux.ibm.com Reported-by: Marc Hartmayer mhartmay@linux.ibm.com Suggested-by: Robin Murphy robin.murphy@arm.com Fixes: 37db8985b211 ("s390/cio: add basic protected virtualization support") Link: https://lore.kernel.org/lkml/20190930153803.7958-1-pasic@linux.ibm.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Cornelia Huck cohuck@redhat.com Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/s390/cio/cio.h | 1 + drivers/s390/cio/css.c | 7 ++++++- drivers/s390/cio/device.c | 2 +- 3 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h index ba7d2480613b9..dcdaba689b20c 100644 --- a/drivers/s390/cio/cio.h +++ b/drivers/s390/cio/cio.h @@ -113,6 +113,7 @@ struct subchannel { enum sch_todo todo; struct work_struct todo_work; struct schib_config config; + u64 dma_mask; char *driver_override; /* Driver name to force a match */ } __attribute__ ((aligned(8)));
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c index 1fbfb0a93f5f1..831850435c23b 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -232,7 +232,12 @@ struct subchannel *css_alloc_subchannel(struct subchannel_id schid, * belong to a subchannel need to fit 31 bit width (e.g. ccw). */ sch->dev.coherent_dma_mask = DMA_BIT_MASK(31); - sch->dev.dma_mask = &sch->dev.coherent_dma_mask; + /* + * But we don't have such restrictions imposed on the stuff that + * is handled by the streaming API. + */ + sch->dma_mask = DMA_BIT_MASK(64); + sch->dev.dma_mask = &sch->dma_mask; return sch;
err: diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c index c421899be20f2..027ef1dde5a7a 100644 --- a/drivers/s390/cio/device.c +++ b/drivers/s390/cio/device.c @@ -710,7 +710,7 @@ static struct ccw_device * io_subchannel_allocate_dev(struct subchannel *sch) if (!cdev->private) goto err_priv; cdev->dev.coherent_dma_mask = sch->dev.coherent_dma_mask; - cdev->dev.dma_mask = &cdev->dev.coherent_dma_mask; + cdev->dev.dma_mask = sch->dev.dma_mask; dma_pool = cio_gp_dma_create(&cdev->dev, 1); if (!dma_pool) goto err_dma_pool;