Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

Pull virtio updates from Michael Tsirkin:
 "Several fixes, most notably fix for virtio on swiotlb systems"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  vhost: silence an unused-variable warning
  virtio: hint if callbacks surprisingly might sleep
  virtio-ccw: wire up ->bus_name callback
  s390/virtio: handle find on invalid queue gracefully
  virtio-ccw: diag 500 may return a negative cookie
  virtio_balloon: remove the unnecessary 0-initialization
  virtio-balloon: improve update_balloon_size_func
  virtio-blk: Consider virtio_max_dma_size() for maximum segment size
  virtio: Introduce virtio_max_dma_size()
  dma: Introduce dma_max_mapping_size()
  swiotlb: Add is_swiotlb_active() function
  swiotlb: Introduce swiotlb_max_mapping_size()

3 files changed, 39 insertions, 0 deletions

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 7ff807f2121c..fcdb23e8d2fc 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -393,3 +393,14 @@ int dma_direct_supported(struct device *dev, u64 mask)
          */
         return mask >= __phys_to_dma(dev, min_mask);
 }
+
+size_t dma_direct_max_mapping_size(struct device *dev)
+{
+        size_t size = SIZE_MAX;
+
+        /* If SWIOTLB is active, use its maximum mapping size */
+        if (is_swiotlb_active())
+                size = swiotlb_max_mapping_size(dev);
+
+        return size;
+}
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index ef2aba503467..c000906348c9 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -360,3 +360,17 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
                 ops->cache_sync(dev, vaddr, size, dir);
 }
 EXPORT_SYMBOL(dma_cache_sync);
+
+size_t dma_max_mapping_size(struct device *dev)
+{
+        const struct dma_map_ops *ops = get_dma_ops(dev);
+        size_t size = SIZE_MAX;
+
+        if (dma_is_direct(ops))
+                size = dma_direct_max_mapping_size(dev);
+        else if (ops && ops->max_mapping_size)
+                size = ops->max_mapping_size(dev);
+
+        return size;
+}
+EXPORT_SYMBOL_GPL(dma_max_mapping_size);
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index a9ad02d4d84e..9f5851064aea 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -666,6 +666,20 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
         return true;
 }
 
+size_t swiotlb_max_mapping_size(struct device *dev)
+{
+        return ((size_t)1 << IO_TLB_SHIFT) * IO_TLB_SEGSIZE;
+}
+
+bool is_swiotlb_active(void)
+{
+        /*
+         * When SWIOTLB is initialized, even if io_tlb_start points to physical
+         * address zero, io_tlb_end surely doesn't.
+         */
+        return io_tlb_end != 0;
+}
+
 #ifdef CONFIG_DEBUG_FS
 
 static int __init swiotlb_create_debugfs(void)