diff options
Diffstat (limited to 'hw/vfio/common.c')
| -rw-r--r-- | hw/vfio/common.c | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/hw/vfio/common.c b/hw/vfio/common.c index 4262b80c44..9c3796e7db 100644 --- a/hw/vfio/common.c +++ b/hw/vfio/common.c @@ -220,7 +220,25 @@ static int vfio_dma_unmap(VFIOContainer *container, .size = size, }; - if (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) { + while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) { + /* + * The type1 backend has an off-by-one bug in the kernel (71a7d3d78e3c + * v4.15) where an overflow in its wrap-around check prevents us from + * unmapping the last page of the address space. Test for the error + * condition and re-try the unmap excluding the last page. The + * expectation is that we've never mapped the last page anyway and this + * unmap request comes via vIOMMU support which also makes it unlikely + * that this page is used. This bug was introduced well after type1 v2 + * support was introduced, so we shouldn't need to test for v1. A fix + * is queued for kernel v5.0 so this workaround can be removed once + * affected kernels are sufficiently deprecated. + */ + if (errno == EINVAL && unmap.size && !(unmap.iova + unmap.size) && + container->iommu_type == VFIO_TYPE1v2_IOMMU) { + trace_vfio_dma_unmap_overflow_workaround(); + unmap.size -= 1ULL << ctz64(container->pgsizes); + continue; + } error_report("VFIO_UNMAP_DMA: %d", -errno); return -errno; } |