From d7b98ae5221007d3f202746903d4c21c7caf7ea9 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 9 Apr 2025 17:15:42 +0200 Subject: dma/contiguous: avoid warning about unused size_bytes When building with W=1, this variable is unused for configs with CONFIG_CMA_SIZE_SEL_PERCENTAGE=y: kernel/dma/contiguous.c:67:26: error: 'size_bytes' defined but not used [-Werror=unused-const-variable=] Change this to a macro to avoid the warning. Fixes: c64be2bb1c6e ("drivers: add Contiguous Memory Allocator") Signed-off-by: Arnd Bergmann Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250409151557.3890443-1-arnd@kernel.org --- kernel/dma/contiguous.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'kernel/dma') diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 055da410ac71..8df0dfaaca18 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -64,8 +64,7 @@ struct cma *dma_contiguous_default_area; * Users, who want to set the size of global CMA area for their system * should use cma= kernel parameter. */ -static const phys_addr_t size_bytes __initconst = - (phys_addr_t)CMA_SIZE_MBYTES * SZ_1M; +#define size_bytes ((phys_addr_t)CMA_SIZE_MBYTES * SZ_1M) static phys_addr_t size_cmdline __initdata = -1; static phys_addr_t base_cmdline __initdata; static phys_addr_t limit_cmdline __initdata; -- cgit v1.2.3 From 2042c352e21d19eaf5f9e22fb6afce72293ef28c Mon Sep 17 00:00:00 2001 From: Balbir Singh Date: Mon, 14 Apr 2025 21:37:52 +1000 Subject: dma/mapping.c: dev_dbg support for dma_addressing_limited MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In the debug and resolution of an issue involving forced use of bounce buffers, 7170130e4c72 ("x86/mm/init: Handle the special case of device private pages in add_pages(), to not increase max_pfn and trigger dma_addressing_limited() bounce buffers"). It would have been easier to debug the issue if dma_addressing_limited() had debug information about the device not being able to address all of memory and thus forcing all accesses through a bounce buffer. Please see[2] Implement dev_dbg to debug the potential use of bounce buffers when we hit the condition. When swiotlb is used, dma_addressing_limited() is used to determine the size of maximum dma buffer size in dma_direct_max_mapping_size(). The debug prints could be triggered in that check as well (when enabled). Link: https://lore.kernel.org/lkml/20250401000752.249348-1-balbirs@nvidia.com/ [1] Link: https://lore.kernel.org/lkml/20250310112206.4168-1-spasswolf@web.de/ [2] Cc: Marek Szyprowski Cc: Robin Murphy Cc: "Christian König" Cc: Ingo Molnar Cc: Kees Cook Cc: Bjorn Helgaas Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Alex Deucher Cc: Bert Karwatzki Cc: Christoph Hellwig Signed-off-by: Balbir Singh Reviewed-by: Christoph Hellwig Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250414113752.3298276-1-balbirs@nvidia.com --- kernel/dma/mapping.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'kernel/dma') diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index cda127027e48..67da08fa6723 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -918,7 +918,7 @@ EXPORT_SYMBOL(dma_set_coherent_mask); * the system, else %false. Lack of addressing bits is the prime reason for * bounce buffering, but might not be the only one. */ -bool dma_addressing_limited(struct device *dev) +static bool __dma_addressing_limited(struct device *dev) { const struct dma_map_ops *ops = get_dma_ops(dev); @@ -930,6 +930,15 @@ bool dma_addressing_limited(struct device *dev) return false; return !dma_direct_all_ram_mapped(dev); } + +bool dma_addressing_limited(struct device *dev) +{ + if (!__dma_addressing_limited(dev)) + return false; + + dev_dbg(dev, "device is DMA addressing limited\n"); + return true; +} EXPORT_SYMBOL_GPL(dma_addressing_limited); size_t dma_max_mapping_size(struct device *dev) -- cgit v1.2.3 From cae5572ec9261f752af834cdaaf5a0ba0afcf256 Mon Sep 17 00:00:00 2001 From: Balbir Singh Date: Tue, 22 Apr 2025 21:40:34 +1000 Subject: dma-mapping: Fix warning reported for missing prototype lkp reported a warning about missing prototype for a recent patch. The kernel-doc style comments are out of sync, move them to the right function. Cc: Marek Szyprowski Cc: Christoph Hellwig Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202504190615.g9fANxHw-lkp@intel.com/ Signed-off-by: Balbir Singh [mszyprow: reformatted subject] Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250422114034.3535515-1-balbirs@nvidia.com --- kernel/dma/mapping.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'kernel/dma') diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 67da08fa6723..051a32988040 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -910,14 +910,6 @@ int dma_set_coherent_mask(struct device *dev, u64 mask) } EXPORT_SYMBOL(dma_set_coherent_mask); -/** - * dma_addressing_limited - return if the device is addressing limited - * @dev: device to check - * - * Return %true if the devices DMA mask is too small to address all memory in - * the system, else %false. Lack of addressing bits is the prime reason for - * bounce buffering, but might not be the only one. - */ static bool __dma_addressing_limited(struct device *dev) { const struct dma_map_ops *ops = get_dma_ops(dev); @@ -931,6 +923,14 @@ static bool __dma_addressing_limited(struct device *dev) return !dma_direct_all_ram_mapped(dev); } +/** + * dma_addressing_limited - return if the device is addressing limited + * @dev: device to check + * + * Return %true if the devices DMA mask is too small to address all memory in + * the system, else %false. Lack of addressing bits is the prime reason for + * bounce buffering, but might not be the only one. + */ bool dma_addressing_limited(struct device *dev) { if (!__dma_addressing_limited(dev)) -- cgit v1.2.3 From 89461db349cc00816c01d55507d511466b3b7151 Mon Sep 17 00:00:00 2001 From: Chen-Yu Tsai Date: Mon, 21 Apr 2025 16:39:29 +0800 Subject: dma-coherent: Warn if OF reserved memory is beyond current coherent DMA mask When a reserved memory region described in the device tree is attached to a device, it is expected that the device's limitations are correctly included in that description. However, if the device driver failed to implement DMA address masking or addressing beyond the default 32 bits (on arm64), then bad things could happen because the DMA address was truncated, such as playing back audio with no actual audio coming out, or DMA overwriting random blocks of kernel memory. Check against the coherent DMA mask when the memory regions are attached to the device. Give a warning when the memory region can not be covered by the mask. A warning instead of a hard error was chosen, because it is possible that existing drivers could be working fine even if they forgot to extend the coherent DMA mask. Signed-off-by: Chen-Yu Tsai Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250421083930.374173-1-wenst@chromium.org --- kernel/dma/coherent.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'kernel/dma') diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c index 3b2bdca9f1d4..77c8d9487a9a 100644 --- a/kernel/dma/coherent.c +++ b/kernel/dma/coherent.c @@ -336,16 +336,22 @@ static phys_addr_t dma_reserved_default_memory_size __initdata; static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev) { - if (!rmem->priv) { - struct dma_coherent_mem *mem; + struct dma_coherent_mem *mem = rmem->priv; + if (!mem) { mem = dma_init_coherent_memory(rmem->base, rmem->base, rmem->size, true); if (IS_ERR(mem)) return PTR_ERR(mem); rmem->priv = mem; } - dma_assign_coherent_memory(dev, rmem->priv); + + /* Warn if the device potentially can't use the reserved memory */ + if (mem->device_base + rmem->size - 1 > + min_not_zero(dev->coherent_dma_mask, dev->bus_dma_limit)) + dev_warn(dev, "reserved memory is beyond device's set DMA address range\n"); + + dma_assign_coherent_memory(dev, mem); return 0; } -- cgit v1.2.3