Re: [PATCH v3 1/1] swiotlb: Reduce swiotlb pool lookups
From: Petr Tesařík
Date: Tue Jul 09 2024 - 05:10:37 EST
On Mon, 8 Jul 2024 12:41:00 -0700
mhkelley58@xxxxxxxxx wrote:
> From: Michael Kelley <mhklinux@xxxxxxxxxxx>
>
> With CONFIG_SWIOTLB_DYNAMIC enabled, each round-trip map/unmap pair
> in the swiotlb results in 6 calls to swiotlb_find_pool(). In multiple
> places, the pool is found and used in one function, and then must
> be found again in the next function that is called because only the
> tlb_addr is passed as an argument. These are the six call sites:
>
> dma_direct_map_page:
> 1. swiotlb_map->swiotlb_tbl_map_single->swiotlb_bounce
>
> dma_direct_unmap_page:
> 2. dma_direct_sync_single_for_cpu->is_swiotlb_buffer
> 3. dma_direct_sync_single_for_cpu->swiotlb_sync_single_for_cpu->
> swiotlb_bounce
> 4. is_swiotlb_buffer
> 5. swiotlb_tbl_unmap_single->swiotlb_del_transient
> 6. swiotlb_tbl_unmap_single->swiotlb_release_slots
>
> Reduce the number of calls by finding the pool at a higher level, and
> passing it as an argument instead of searching again. A key change is
> for is_swiotlb_buffer() to return a pool pointer instead of a boolean,
> and then pass this pool pointer to subsequent swiotlb functions.
>
> There are 9 occurrences of is_swiotlb_buffer() used to test if a buffer
> is a swiotlb buffer before calling a swiotlb function. To reduce code
> duplication in getting the pool pointer and passing it as an argument,
> introduce inline wrappers for this pattern. The generated code is
> essentially unchanged.
>
> Since is_swiotlb_buffer() no longer returns a boolean, rename some
> functions to reflect the change:
> * swiotlb_find_pool() becomes __swiotlb_find_pool()
> * is_swiotlb_buffer() becomes swiotlb_find_pool()
> * is_xen_swiotlb_buffer() becomes xen_swiotlb_find_pool()
>
> With these changes, a round-trip map/unmap pair requires only 2 pool
> lookups (listed using the new names and wrappers):
>
> dma_direct_unmap_page:
> 1. dma_direct_sync_single_for_cpu->swiotlb_find_pool
> 2. swiotlb_tbl_unmap_single->swiotlb_find_pool
>
> These changes come from noticing the inefficiencies in a code review,
> not from performance measurements. With CONFIG_SWIOTLB_DYNAMIC,
> __swiotlb_find_pool() is not trivial, and it uses an RCU read lock,
> so avoiding the redundant calls helps performance in a hot path.
> When CONFIG_SWIOTLB_DYNAMIC is *not* set, the code size reduction
> is minimal and the perf benefits are likely negligible, but no
> harm is done.
>
> No functional change is intended.
>
> Signed-off-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Reviewed-by: Petr Tesarik <petr@xxxxxxxxxxx>
Find a few notes inline, mostly FYI:
> ---
>
> Changes in v3:
> * Add inline wrappers for swiotlb_tbl_unmap_single(),
> swiotlb_sync_single_for_device() and swiotlb_sync_single_for_cpu() to
> commonize the swiotlb_find_pool() tests for whether the buffer is a
> swiotlb buffer [Christoph Hellwig]
> * Change most users of __swiotlb_find_pool() to use swiotlb_find_pool(),
> as the extra checks in the latter aren't impactful. Remove v2 change in
> swiotlb_find_pool() to use __swiotlb_find_pool() when
> CONFIG_SWIOTLB_DYNAMIC is not set. [Christoph Hellwig]
> * Rework swiotlb_find_pool() to use IS_ENABLED() instead of #ifdef's.
> To make this work, move dma_uses_io_tlb field in struct device out from
> under #ifdef CONFIG_SWIOTLB_DYNAMIC. [Christoph Hellwig]
> * Fix line lengths > 80 chars [Christoph Hellwig]
> * Update commit message to reflect changes
>
> Changes in v2 vs. RFC version[1]:
> * In swiotlb_find_pool(), use __swiotlb_find_pool() instead of open
> coding when CONFIG_SWIOTLB_DYNAMIC is not set [Petr Tesařík]
> * Rename functions as described in the commit message to reflect that
> is_swiotlb_buffer() no longer returns a boolean [Petr Tesařík,
> Christoph Hellwig]
> * Updated commit message and patch Subject
>
> [1] https://lore.kernel.org/linux-iommu/20240607031421.182589-1-mhklinux@xxxxxxxxxxx/
>
> drivers/iommu/dma-iommu.c | 11 ++-
> drivers/xen/swiotlb-xen.c | 31 +++++---
> include/linux/device.h | 3 +-
> include/linux/scatterlist.h | 2 +-
> include/linux/swiotlb.h | 138 +++++++++++++++++++++---------------
> kernel/dma/direct.c | 10 +--
> kernel/dma/direct.h | 9 +--
> kernel/dma/swiotlb.c | 64 +++++++++--------
> 8 files changed, 150 insertions(+), 118 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 43520e7275cc..7b4486238427 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1081,8 +1081,7 @@ static void iommu_dma_sync_single_for_cpu(struct device *dev,
> if (!dev_is_dma_coherent(dev))
> arch_sync_dma_for_cpu(phys, size, dir);
>
> - if (is_swiotlb_buffer(dev, phys))
> - swiotlb_sync_single_for_cpu(dev, phys, size, dir);
> + swiotlb_sync_single_for_cpu(dev, phys, size, dir);
> }
>
> static void iommu_dma_sync_single_for_device(struct device *dev,
> @@ -1094,8 +1093,7 @@ static void iommu_dma_sync_single_for_device(struct device *dev,
> return;
>
> phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);
> - if (is_swiotlb_buffer(dev, phys))
> - swiotlb_sync_single_for_device(dev, phys, size, dir);
> + swiotlb_sync_single_for_device(dev, phys, size, dir);
>
> if (!dev_is_dma_coherent(dev))
> arch_sync_dma_for_device(phys, size, dir);
> @@ -1189,7 +1187,7 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> arch_sync_dma_for_device(phys, size, dir);
>
> iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
> - if (iova == DMA_MAPPING_ERROR && is_swiotlb_buffer(dev, phys))
> + if (iova == DMA_MAPPING_ERROR)
> swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> return iova;
> }
> @@ -1209,8 +1207,7 @@ static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
>
> __iommu_dma_unmap(dev, dma_handle, size);
>
> - if (unlikely(is_swiotlb_buffer(dev, phys)))
> - swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> + swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
> }
>
> /*
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 6579ae3f6dac..35155258a7e2 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -88,7 +88,8 @@ static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
> return 0;
> }
>
> -static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr)
> +static struct io_tlb_pool *xen_swiotlb_find_pool(struct device *dev,
> + dma_addr_t dma_addr)
> {
> unsigned long bfn = XEN_PFN_DOWN(dma_to_phys(dev, dma_addr));
> unsigned long xen_pfn = bfn_to_local_pfn(bfn);
> @@ -99,8 +100,8 @@ static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr)
> * in our domain. Therefore _only_ check address within our domain.
> */
> if (pfn_valid(PFN_DOWN(paddr)))
> - return is_swiotlb_buffer(dev, paddr);
> - return 0;
> + return swiotlb_find_pool(dev, paddr);
> + return NULL;
> }
>
> #ifdef CONFIG_X86
> @@ -227,8 +228,9 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
> * Ensure that the address returned is DMA'ble
> */
> if (unlikely(!dma_capable(dev, dev_addr, size, true))) {
> - swiotlb_tbl_unmap_single(dev, map, size, dir,
> - attrs | DMA_ATTR_SKIP_CPU_SYNC);
> + __swiotlb_tbl_unmap_single(dev, map, size, dir,
> + attrs | DMA_ATTR_SKIP_CPU_SYNC,
> + swiotlb_find_pool(dev, map));
> return DMA_MAPPING_ERROR;
> }
>
> @@ -254,6 +256,7 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
> size_t size, enum dma_data_direction dir, unsigned long attrs)
> {
> phys_addr_t paddr = xen_dma_to_phys(hwdev, dev_addr);
> + struct io_tlb_pool *pool;
>
> BUG_ON(dir == DMA_NONE);
>
> @@ -265,8 +268,10 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
> }
>
> /* NOTE: We use dev_addr here, not paddr! */
> - if (is_xen_swiotlb_buffer(hwdev, dev_addr))
> - swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs);
> + pool = xen_swiotlb_find_pool(hwdev, dev_addr);
> + if (pool)
> + __swiotlb_tbl_unmap_single(hwdev, paddr, size, dir,
> + attrs, pool);
> }
>
> static void
> @@ -274,6 +279,7 @@ xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
> size_t size, enum dma_data_direction dir)
> {
> phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
> + struct io_tlb_pool *pool;
>
> if (!dev_is_dma_coherent(dev)) {
> if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
> @@ -282,8 +288,9 @@ xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
> xen_dma_sync_for_cpu(dev, dma_addr, size, dir);
> }
>
> - if (is_xen_swiotlb_buffer(dev, dma_addr))
> - swiotlb_sync_single_for_cpu(dev, paddr, size, dir);
> + pool = xen_swiotlb_find_pool(dev, dma_addr);
> + if (pool)
> + __swiotlb_sync_single_for_cpu(dev, paddr, size, dir, pool);
Since swiotlb_sync_single_for_cpu() adds an unlikely() to the
condition, do we also want to add it here?
> }
>
> static void
> @@ -291,9 +298,11 @@ xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
> size_t size, enum dma_data_direction dir)
> {
> phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
> + struct io_tlb_pool *pool;
>
> - if (is_xen_swiotlb_buffer(dev, dma_addr))
> - swiotlb_sync_single_for_device(dev, paddr, size, dir);
> + pool = xen_swiotlb_find_pool(dev, dma_addr);
> + if (pool)
> + __swiotlb_sync_single_for_device(dev, paddr, size, dir, pool);
Same as above, but with swiotlb_sync_single_for_device().
>
> if (!dev_is_dma_coherent(dev)) {
> if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
> diff --git a/include/linux/device.h b/include/linux/device.h
> index ace039151cb8..d8a7f5245b7e 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -778,8 +778,9 @@ struct device {
> #ifdef CONFIG_SWIOTLB_DYNAMIC
> struct list_head dma_io_tlb_pools;
> spinlock_t dma_io_tlb_lock;
> - bool dma_uses_io_tlb;
> #endif
> + bool dma_uses_io_tlb;
> +
This field is unsued and always false if !CONFIG_SWIOTLB_DYNAMIC. This
works as expected but it had better be mentioned in the documentation of
the field so people are not confused.
Update: If hch keeps the field inside #ifdef, this is now moot.
> /* arch specific additions */
> struct dev_archdata archdata;
>
> diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
> index 77df3d7b18a6..e61d164622db 100644
> --- a/include/linux/scatterlist.h
> +++ b/include/linux/scatterlist.h
> @@ -332,7 +332,7 @@ static inline void sg_dma_unmark_bus_address(struct scatterlist *sg)
> * Description:
> * Returns true if the scatterlist was marked for SWIOTLB bouncing. Not all
> * elements may have been bounced, so the caller would have to check
> - * individual SG entries with is_swiotlb_buffer().
> + * individual SG entries with swiotlb_find_pool().
> */
> static inline bool sg_dma_is_swiotlb(struct scatterlist *sg)
> {
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index 14bc10c1bb23..9ee8231e6956 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -42,24 +42,6 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
> int (*remap)(void *tlb, unsigned long nslabs));
> extern void __init swiotlb_update_mem_attributes(void);
>
> -phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, phys_addr_t phys,
> - size_t mapping_size,
> - unsigned int alloc_aligned_mask, enum dma_data_direction dir,
> - unsigned long attrs);
> -
> -extern void swiotlb_tbl_unmap_single(struct device *hwdev,
> - phys_addr_t tlb_addr,
> - size_t mapping_size,
> - enum dma_data_direction dir,
> - unsigned long attrs);
> -
> -void swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr,
> - size_t size, enum dma_data_direction dir);
> -void swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr,
> - size_t size, enum dma_data_direction dir);
> -dma_addr_t swiotlb_map(struct device *dev, phys_addr_t phys,
> - size_t size, enum dma_data_direction dir, unsigned long attrs);
> -
> #ifdef CONFIG_SWIOTLB
>
> /**
> @@ -143,55 +125,48 @@ struct io_tlb_mem {
> #endif
> };
>
> -#ifdef CONFIG_SWIOTLB_DYNAMIC
> -
> -struct io_tlb_pool *swiotlb_find_pool(struct device *dev, phys_addr_t paddr);
> -
> -#else
> -
> -static inline struct io_tlb_pool *swiotlb_find_pool(struct device *dev,
> - phys_addr_t paddr)
> -{
> - return &dev->dma_io_tlb_mem->defpool;
> -}
> -
> -#endif
> +struct io_tlb_pool *__swiotlb_find_pool(struct device *dev, phys_addr_t paddr);
>
> /**
> - * is_swiotlb_buffer() - check if a physical address belongs to a swiotlb
> + * swiotlb_find_pool() - find swiotlb pool to which a physical address belongs
> * @dev: Device which has mapped the buffer.
> * @paddr: Physical address within the DMA buffer.
> *
> - * Check if @paddr points into a bounce buffer.
> + * Find the swiotlb pool that @paddr points into.
> *
> * Return:
> - * * %true if @paddr points into a bounce buffer
> - * * %false otherwise
> + * * pool address if @paddr points into a bounce buffer
> + * * NULL if @paddr does not point into a bounce buffer. As such, this function
> + * can be used to determine if @paddr denotes a swiotlb bounce buffer.
> */
> -static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
> +static inline struct io_tlb_pool *swiotlb_find_pool(struct device *dev,
> + phys_addr_t paddr)
> {
> struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
>
> if (!mem)
> - return false;
> + return NULL;
> +
> + if (IS_ENABLED(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();
> + if (READ_ONCE(dev->dma_uses_io_tlb))
> + return __swiotlb_find_pool(dev, paddr);
OK, so __swiotlb_find_pool() is now always declared (so the code
compiles), but if CONFIG_SWIOTLB_DYNAMIC=n, it is never defined. The
result still links, because the compiler optimizes away the whole
if-clause, so there are no references to an undefined symbol in the
object file.
I think I've already seen similar constructs elsewhere in the kernel,
so relying on the optimization seems to be common practice.
> + } else if (paddr >= mem->defpool.start && paddr < mem->defpool.end) {
> + return &mem->defpool;
> + }
>
> -#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
> + return NULL;
> }
>
> static inline bool is_swiotlb_force_bounce(struct device *dev)
> @@ -219,9 +194,10 @@ static inline void swiotlb_dev_init(struct device *dev)
> {
> }
>
> -static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
> +static inline struct io_tlb_pool *swiotlb_find_pool(struct device *dev,
> + phys_addr_t paddr)
> {
> - return false;
> + return NULL;
> }
> static inline bool is_swiotlb_force_bounce(struct device *dev)
> {
> @@ -260,6 +236,56 @@ static inline phys_addr_t default_swiotlb_limit(void)
> }
> #endif /* CONFIG_SWIOTLB */
>
> +phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, phys_addr_t phys,
> + size_t mapping_size,
> + unsigned int alloc_aligned_mask, enum dma_data_direction dir,
> + unsigned long attrs);
> +
> +void __swiotlb_tbl_unmap_single(struct device *hwdev,
> + phys_addr_t tlb_addr,
> + size_t mapping_size,
> + enum dma_data_direction dir,
> + unsigned long attrs,
> + struct io_tlb_pool *pool);
> +
> +void __swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr,
> + size_t size, enum dma_data_direction dir,
> + struct io_tlb_pool *pool);
> +void __swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr,
> + size_t size, enum dma_data_direction dir,
> + struct io_tlb_pool *pool);
> +dma_addr_t swiotlb_map(struct device *dev, phys_addr_t phys,
> + size_t size, enum dma_data_direction dir, unsigned long attrs);
> +
> +
> +static inline void swiotlb_tbl_unmap_single(struct device *dev,
> + phys_addr_t addr, size_t size,
> + enum dma_data_direction dir, unsigned long attrs)
> +{
> + struct io_tlb_pool *pool = swiotlb_find_pool(dev, addr);
> +
> + if (unlikely(pool))
> + __swiotlb_tbl_unmap_single(dev, addr, size, dir, attrs, pool);
> +}
> +
> +static inline void swiotlb_sync_single_for_device(struct device *dev,
> + phys_addr_t addr, size_t size, enum dma_data_direction dir)
> +{
> + struct io_tlb_pool *pool = swiotlb_find_pool(dev, addr);
> +
> + if (unlikely(pool))
> + __swiotlb_sync_single_for_device(dev, addr, size, dir, pool);
We're adding an unlikely() here, which wasn't originally present in
iommu_dma_sync_single_for_device(). OTOH it should do no harm, and it
was most likely an omission.
> +}
> +
> +static inline void swiotlb_sync_single_for_cpu(struct device *dev,
> + phys_addr_t addr, size_t size, enum dma_data_direction dir)
> +{
> + struct io_tlb_pool *pool = swiotlb_find_pool(dev, addr);
> +
> + if (unlikely(pool))
> + __swiotlb_sync_single_for_cpu(dev, addr, size, dir, pool);
Same as above, but for iommu_dma_sync_single_for_cpu().
Again, none of my comments should block inclusion.
Petr T
> +}
> +
> extern void swiotlb_print_info(void);
>
> #ifdef CONFIG_DMA_RESTRICTED_POOL
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index 4d543b1e9d57..4480a3cd92e0 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -404,9 +404,7 @@ void dma_direct_sync_sg_for_device(struct device *dev,
> for_each_sg(sgl, sg, nents, i) {
> phys_addr_t paddr = dma_to_phys(dev, sg_dma_address(sg));
>
> - if (unlikely(is_swiotlb_buffer(dev, paddr)))
> - swiotlb_sync_single_for_device(dev, paddr, sg->length,
> - dir);
> + swiotlb_sync_single_for_device(dev, paddr, sg->length, dir);
>
> if (!dev_is_dma_coherent(dev))
> arch_sync_dma_for_device(paddr, sg->length,
> @@ -430,9 +428,7 @@ void dma_direct_sync_sg_for_cpu(struct device *dev,
> if (!dev_is_dma_coherent(dev))
> arch_sync_dma_for_cpu(paddr, sg->length, dir);
>
> - if (unlikely(is_swiotlb_buffer(dev, paddr)))
> - swiotlb_sync_single_for_cpu(dev, paddr, sg->length,
> - dir);
> + swiotlb_sync_single_for_cpu(dev, paddr, sg->length, dir);
>
> if (dir == DMA_FROM_DEVICE)
> arch_dma_mark_clean(paddr, sg->length);
> @@ -640,7 +636,7 @@ size_t dma_direct_max_mapping_size(struct device *dev)
> bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr)
> {
> return !dev_is_dma_coherent(dev) ||
> - is_swiotlb_buffer(dev, dma_to_phys(dev, dma_addr));
> + swiotlb_find_pool(dev, dma_to_phys(dev, dma_addr));
> }
>
> /**
> diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
> index 18d346118fe8..d2c0b7e632fc 100644
> --- a/kernel/dma/direct.h
> +++ b/kernel/dma/direct.h
> @@ -58,8 +58,7 @@ static inline void dma_direct_sync_single_for_device(struct device *dev,
> {
> phys_addr_t paddr = dma_to_phys(dev, addr);
>
> - if (unlikely(is_swiotlb_buffer(dev, paddr)))
> - swiotlb_sync_single_for_device(dev, paddr, size, dir);
> + swiotlb_sync_single_for_device(dev, paddr, size, dir);
>
> if (!dev_is_dma_coherent(dev))
> arch_sync_dma_for_device(paddr, size, dir);
> @@ -75,8 +74,7 @@ static inline void dma_direct_sync_single_for_cpu(struct device *dev,
> arch_sync_dma_for_cpu_all();
> }
>
> - if (unlikely(is_swiotlb_buffer(dev, paddr)))
> - swiotlb_sync_single_for_cpu(dev, paddr, size, dir);
> + swiotlb_sync_single_for_cpu(dev, paddr, size, dir);
>
> if (dir == DMA_FROM_DEVICE)
> arch_dma_mark_clean(paddr, size);
> @@ -121,8 +119,7 @@ static inline void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
> if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
> dma_direct_sync_single_for_cpu(dev, addr, size, dir);
>
> - if (unlikely(is_swiotlb_buffer(dev, phys)))
> - swiotlb_tbl_unmap_single(dev, phys, size, dir,
> + swiotlb_tbl_unmap_single(dev, phys, size, dir,
> attrs | DMA_ATTR_SKIP_CPU_SYNC);
> }
> #endif /* _KERNEL_DMA_DIRECT_H */
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index fe1ccb53596f..5010812e7da4 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -763,16 +763,18 @@ static void swiotlb_dyn_free(struct rcu_head *rcu)
> }
>
> /**
> - * swiotlb_find_pool() - find the IO TLB pool for a physical address
> + * __swiotlb_find_pool() - find the IO TLB pool for a physical address
> * @dev: Device which has mapped the DMA buffer.
> * @paddr: Physical address within the DMA buffer.
> *
> * Find the IO TLB memory pool descriptor which contains the given physical
> - * address, if any.
> + * address, if any. This function is for use only when the dev is known to
> + * be using swiotlb. Use swiotlb_find_pool() for the more general case
> + * when this condition is not met.
> *
> * Return: Memory pool which contains @paddr, or %NULL if none.
> */
> -struct io_tlb_pool *swiotlb_find_pool(struct device *dev, phys_addr_t paddr)
> +struct io_tlb_pool *__swiotlb_find_pool(struct device *dev, phys_addr_t paddr)
> {
> struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
> struct io_tlb_pool *pool;
> @@ -855,9 +857,8 @@ static unsigned int swiotlb_align_offset(struct device *dev,
> * Bounce: copy the swiotlb buffer from or back to the original dma location
> */
> static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size,
> - enum dma_data_direction dir)
> + enum dma_data_direction dir, struct io_tlb_pool *mem)
> {
> - struct io_tlb_pool *mem = swiotlb_find_pool(dev, tlb_addr);
> int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
> phys_addr_t orig_addr = mem->slots[index].orig_addr;
> size_t alloc_size = mem->slots[index].alloc_size;
> @@ -1243,7 +1244,7 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
> * that was made by swiotlb_dyn_alloc() on a third CPU (cf. multicopy
> * atomicity).
> *
> - * See also the comment in is_swiotlb_buffer().
> + * See also the comment in swiotlb_find_pool().
> */
> smp_mb();
>
> @@ -1435,13 +1436,13 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
> * hardware behavior. Use of swiotlb is supposed to be transparent,
> * i.e. swiotlb must not corrupt memory by clobbering unwritten bytes.
> */
> - swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
> + swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE, pool);
> return tlb_addr;
> }
>
> -static void swiotlb_release_slots(struct device *dev, phys_addr_t tlb_addr)
> +static void swiotlb_release_slots(struct device *dev, phys_addr_t tlb_addr,
> + struct io_tlb_pool *mem)
> {
> - struct io_tlb_pool *mem = swiotlb_find_pool(dev, tlb_addr);
> unsigned long flags;
> unsigned int offset = swiotlb_align_offset(dev, 0, tlb_addr);
> int index, nslots, aindex;
> @@ -1505,11 +1506,9 @@ static void swiotlb_release_slots(struct device *dev, phys_addr_t tlb_addr)
> *
> * Return: %true if @tlb_addr belonged to a transient pool that was released.
> */
> -static bool swiotlb_del_transient(struct device *dev, phys_addr_t tlb_addr)
> +static bool swiotlb_del_transient(struct device *dev, phys_addr_t tlb_addr,
> + struct io_tlb_pool *pool)
> {
> - struct io_tlb_pool *pool;
> -
> - pool = swiotlb_find_pool(dev, tlb_addr);
> if (!pool->transient)
> return false;
>
> @@ -1522,7 +1521,8 @@ static bool swiotlb_del_transient(struct device *dev, phys_addr_t tlb_addr)
> #else /* !CONFIG_SWIOTLB_DYNAMIC */
>
> static inline bool swiotlb_del_transient(struct device *dev,
> - phys_addr_t tlb_addr)
> + phys_addr_t tlb_addr,
> + struct io_tlb_pool *pool)
> {
> return false;
> }
> @@ -1532,36 +1532,39 @@ static inline bool swiotlb_del_transient(struct device *dev,
> /*
> * tlb_addr is the physical address of the bounce buffer to unmap.
> */
> -void swiotlb_tbl_unmap_single(struct device *dev, phys_addr_t tlb_addr,
> +void __swiotlb_tbl_unmap_single(struct device *dev, phys_addr_t tlb_addr,
> size_t mapping_size, enum dma_data_direction dir,
> - unsigned long attrs)
> + unsigned long attrs, struct io_tlb_pool *pool)
> {
> /*
> * First, sync the memory before unmapping the entry
> */
> if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
> (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
> - swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_FROM_DEVICE);
> + swiotlb_bounce(dev, tlb_addr, mapping_size,
> + DMA_FROM_DEVICE, pool);
>
> - if (swiotlb_del_transient(dev, tlb_addr))
> + if (swiotlb_del_transient(dev, tlb_addr, pool))
> return;
> - swiotlb_release_slots(dev, tlb_addr);
> + swiotlb_release_slots(dev, tlb_addr, pool);
> }
>
> -void swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr,
> - size_t size, enum dma_data_direction dir)
> +void __swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr,
> + size_t size, enum dma_data_direction dir,
> + struct io_tlb_pool *pool)
> {
> if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
> - swiotlb_bounce(dev, tlb_addr, size, DMA_TO_DEVICE);
> + swiotlb_bounce(dev, tlb_addr, size, DMA_TO_DEVICE, pool);
> else
> BUG_ON(dir != DMA_FROM_DEVICE);
> }
>
> -void swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr,
> - size_t size, enum dma_data_direction dir)
> +void __swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr,
> + size_t size, enum dma_data_direction dir,
> + struct io_tlb_pool *pool)
> {
> if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
> - swiotlb_bounce(dev, tlb_addr, size, DMA_FROM_DEVICE);
> + swiotlb_bounce(dev, tlb_addr, size, DMA_FROM_DEVICE, pool);
> else
> BUG_ON(dir != DMA_TO_DEVICE);
> }
> @@ -1585,8 +1588,9 @@ dma_addr_t swiotlb_map(struct device *dev, phys_addr_t paddr, size_t size,
> /* Ensure that the address returned is DMA'ble */
> dma_addr = phys_to_dma_unencrypted(dev, swiotlb_addr);
> if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
> - swiotlb_tbl_unmap_single(dev, swiotlb_addr, size, dir,
> - attrs | DMA_ATTR_SKIP_CPU_SYNC);
> + __swiotlb_tbl_unmap_single(dev, swiotlb_addr, size, dir,
> + attrs | DMA_ATTR_SKIP_CPU_SYNC,
> + swiotlb_find_pool(dev, swiotlb_addr));
> dev_WARN_ONCE(dev, 1,
> "swiotlb addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
> &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
> @@ -1774,11 +1778,13 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
> bool swiotlb_free(struct device *dev, struct page *page, size_t size)
> {
> phys_addr_t tlb_addr = page_to_phys(page);
> + struct io_tlb_pool *pool;
>
> - if (!is_swiotlb_buffer(dev, tlb_addr))
> + pool = swiotlb_find_pool(dev, tlb_addr);
> + if (!pool)
> return false;
>
> - swiotlb_release_slots(dev, tlb_addr);
> + swiotlb_release_slots(dev, tlb_addr, pool);
>
> return true;
> }