Merge tag 'dma-mapping-6.6-2023-09-30' of git://git.infradead.org/users/hch/dma-mapping

Pull dma-mapping fixes from Christoph Hellwig:

 - fix the narea calculation in swiotlb initialization (Ross Lagerwall)

 - fix the check whether a device has used swiotlb (Petr Tesarik)

* tag 'dma-mapping-6.6-2023-09-30' of git://git.infradead.org/users/hch/dma-mapping:
  swiotlb: fix the check whether a device has used software IO TLB
  swiotlb: use the calculated number of areas

1 files changed, 16 insertions, 7 deletions

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index b4536626f8ff..ecde0312dd52 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -172,14 +172,23 @@ static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
 	if (!mem)
 		return false;
 
-	if (IS_ENABLED(CONFIG_SWIOTLB_DYNAMIC)) {
-		/* Pairs with smp_wmb() in swiotlb_find_slots() and
-		 * swiotlb_dyn_alloc(), which modify the RCU lists.
-		 */
-		smp_rmb();
-		return swiotlb_find_pool(dev, paddr);
-	}
+#ifdef CONFIG_SWIOTLB_DYNAMIC
+	/*
+	 * All SWIOTLB buffer addresses must have been returned by
+	 * swiotlb_tbl_map_single() and passed to a device driver.
+	 * If a SWIOTLB address is checked on another CPU, then it was
+	 * presumably loaded by the device driver from an unspecified private
+	 * data structure. Make sure that this load is ordered before reading
+	 * dev->dma_uses_io_tlb here and mem->pools in swiotlb_find_pool().
+	 *
+	 * This barrier pairs with smp_mb() in swiotlb_find_slots().
+	 */
+	smp_rmb();
+	return READ_ONCE(dev->dma_uses_io_tlb) &&
+		swiotlb_find_pool(dev, paddr);
+#else
 	return paddr >= mem->defpool.start && paddr < mem->defpool.end;
+#endif
 }
 
 static inline bool is_swiotlb_force_bounce(struct device *dev)