Commit 3b517966 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 25d48d57 2d5780bb

include/linux/swiotlb.h

+16 −7
Original line number Diff line number Diff line
@@ -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.

#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 swiotlb_find_pool(dev, paddr);

	}

	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)

kernel/dma/swiotlb.c

+22 −9
Original line number Diff line number Diff line
@@ -399,14 +399,13 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags, 
	}



	mem->areas = memblock_alloc(array_size(sizeof(struct io_tlb_area),

		default_nareas), SMP_CACHE_BYTES);

		nareas), SMP_CACHE_BYTES);

	if (!mem->areas) {

		pr_warn("%s: Failed to allocate mem->areas.\n", __func__);

		return;

	}



	swiotlb_init_io_tlb_pool(mem, __pa(tlb), nslabs, false,

				 default_nareas);

	swiotlb_init_io_tlb_pool(mem, __pa(tlb), nslabs, false, nareas);

	add_mem_pool(&io_tlb_default_mem, mem);



	if (flags & SWIOTLB_VERBOSE)
@@ -729,9 +728,6 @@ static void swiotlb_dyn_alloc(struct work_struct *work) 
	}



	add_mem_pool(mem, pool);



	/* Pairs with smp_rmb() in is_swiotlb_buffer(). */

	smp_wmb();

}



/**
@@ -1152,9 +1148,26 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr, 
	spin_unlock_irqrestore(&dev->dma_io_tlb_lock, flags);



found:

	dev->dma_uses_io_tlb = true;

	/* Pairs with smp_rmb() in is_swiotlb_buffer() */

	smp_wmb();

	WRITE_ONCE(dev->dma_uses_io_tlb, true);



	/*

	 * The general barrier orders reads and writes against a presumed store

	 * of the SWIOTLB buffer address by a device driver (to a driver private

	 * data structure). It serves two purposes.

	 *

	 * First, the store to dev->dma_uses_io_tlb must be ordered before the

	 * presumed store. This guarantees that the returned buffer address

	 * cannot be passed to another CPU before updating dev->dma_uses_io_tlb.

	 *

	 * Second, the load from mem->pools must be ordered before the same

	 * presumed store. This guarantees that the returned buffer address

	 * cannot be observed by another CPU before an update of the RCU list

	 * that was made by swiotlb_dyn_alloc() on a third CPU (cf. multicopy

	 * atomicity).

	 *

	 * See also the comment in is_swiotlb_buffer().

	 */

	smp_mb();



	*retpool = pool;

	return index;