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 <robin.murphy@arm.com>
Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
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 4d0f545fb3ec5a1750d9112a851deb8fd976d32d..8e717a587870fde6f600b6aaf9ffab5f6ef017cf 100644 (file)
--- 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 c9fa0a922cba94ab43dd2690c7970ff5baca0fd3..0a4ba21a57a7c29de184478612411f57fa8a59bb 100644 (file)
--- 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=
-         <node>:size[,<node>:size]" on the kernel's command line.
+         <node>:size[,<node>: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 799f6e9c88bd6ca784621f16736e42ac95edb04f..f754079a287d615c4a9926bf67dcd2ed2c3cb8f5 100644 (file)
--- 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;