From: Feng Tang Date: Mon, 25 May 2026 01:51:11 +0000 (+0800) Subject: dma-contiguous: simplify numa cma area handling X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d5cae2261b86913e602452ce4a07e6aefc0f603b;p=thirdparty%2Fkernel%2Flinux.git dma-contiguous: simplify numa cma area handling Currently, there are 2 kernel cmdline ways to setup numa cma area: "cma_pernuma=" and "numa_cma=", and there are 2 cma arrays as well, while they have no difference technically. Robin suggested to cleanup the code and only use one array [1], as "the apparent intent that users only want one _or_ the other". Simplify the code by only using one array to save the numa cma area. And in rare case that a user really setup the 2 cmdline parameters at the same time, let the per-node specific size setting 'numa_cma=' take priority over the global numa cma setting. Link[1]: https://lore.kernel.org/lkml/43c5301c-fe6a-41e4-9482-ccfc7b62f2a7@arm.com/ Suggested-by: Robin Murphy Signed-off-by: Feng Tang Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20260525015111.6267-1-feng.tang@linux.alibaba.com --- diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 4d0f545fb3ec5..8e717a587870f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -895,6 +895,10 @@ Kernel parameters contiguous memory allocations. It will reserve CMA area for the specified node. + If it is setup together with upper 'cmd_pernuma=' + (unlikely), its size setting takes priority for the + specified numa nodes. + With numa CMA enabled, DMA users on node nid will first try to allocate buffer from the numa area which is located in node nid, if the allocation fails, diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index c9fa0a922cba9..0a4ba21a57a7c 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -179,7 +179,9 @@ config DMA_NUMA_CMA You can set the size of pernuma CMA by specifying "cma_pernuma=size" or set the node id and its size of CMA by specifying "numa_cma= - :size[,:size]" on the kernel's command line. + :size[,:size]" on the kernel's command line. And in + rare case that the above 2 are both setup, then the "numa_cma=" + takes priority for the specified numa nodes. config CMA_SIZE_PERNUMA bool "Default CMA area per NUMA node" diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 799f6e9c88bd6..f754079a287d6 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -134,7 +134,6 @@ EXPORT_SYMBOL_GPL(dev_get_cma_area); static struct cma *dma_contiguous_numa_area[MAX_NUMNODES]; static phys_addr_t numa_cma_size[MAX_NUMNODES] __initdata; -static struct cma *dma_contiguous_pernuma_area[MAX_NUMNODES]; static phys_addr_t pernuma_size_bytes __initdata; static bool numa_cma_configured __initdata; @@ -208,7 +207,7 @@ static void __init dma_numa_cma_reserve(void) pernuma_size_bytes = cma_get_size(dma_contiguous_default_area); for_each_node(nid) { - int ret; + int size, ret; char name[CMA_MAX_NAME]; struct cma **cma; @@ -218,27 +217,17 @@ static void __init dma_numa_cma_reserve(void) continue; } - if (pernuma_size_bytes) { - - cma = &dma_contiguous_pernuma_area[nid]; - snprintf(name, sizeof(name), "pernuma%d", nid); - ret = cma_declare_contiguous_nid(0, pernuma_size_bytes, 0, 0, - 0, false, name, cma, nid); - if (ret) - pr_warn("%s: reservation failed: err %d, node %d", __func__, - ret, nid); - } - - if (numa_cma_size[nid]) { + /* per-node numa setting has the priority */ + size = numa_cma_size[nid] ?: pernuma_size_bytes; + if (!size) + continue; - cma = &dma_contiguous_numa_area[nid]; - snprintf(name, sizeof(name), "numa%d", nid); - ret = cma_declare_contiguous_nid(0, numa_cma_size[nid], 0, 0, 0, false, - name, cma, nid); - if (ret) - pr_warn("%s: reservation failed: err %d, node %d", __func__, - ret, nid); - } + cma = &dma_contiguous_numa_area[nid]; + snprintf(name, sizeof(name), "numa%d", nid); + ret = cma_declare_contiguous_nid(0, size, 0, 0, 0, false, name, cma, nid); + if (ret) + pr_warn("%s: reservation failed: err %d, node %d", __func__, + ret, nid); } } #else @@ -437,16 +426,8 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp) #ifdef CONFIG_DMA_NUMA_CMA if (nid != NUMA_NO_NODE && !(gfp & (GFP_DMA | GFP_DMA32))) { - struct cma *cma = dma_contiguous_pernuma_area[nid]; + struct cma *cma = dma_contiguous_numa_area[nid]; struct page *page; - - if (cma) { - page = cma_alloc_aligned(cma, size, gfp); - if (page) - return page; - } - - cma = dma_contiguous_numa_area[nid]; if (cma) { page = cma_alloc_aligned(cma, size, gfp); if (page) @@ -484,9 +465,6 @@ void dma_free_contiguous(struct device *dev, struct page *page, size_t size) * otherwise, page is from either per-numa cma or default cma */ #ifdef CONFIG_DMA_NUMA_CMA - if (cma_release(dma_contiguous_pernuma_area[page_to_nid(page)], - page, count)) - return; if (cma_release(dma_contiguous_numa_area[page_to_nid(page)], page, count)) return;