Re: [PATCH v7 04/15] swiotlb: Add restricted DMA pool initialization

On Thu, May 20, 2021 at 2:54 AM Florian Fainelli [off-list ref] wrote:

On 5/17/2021 11:42 PM, Claire Chang wrote:

quoted

Add the initialization function to create restricted DMA pools from
matching reserved-memory nodes.

Signed-off-by: Claire Chang <redacted>
---
 include/linux/device.h  |  4 +++
 include/linux/swiotlb.h |  3 +-
 kernel/dma/swiotlb.c    | 76 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index 38a2071cf776..4987608ea4ff 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h

@@ -416,6 +416,7 @@ struct dev_links_info {
  * @dma_pools:       Dma pools (if dma'ble device).
  * @dma_mem: Internal for coherent mem override.
  * @cma_area:        Contiguous memory area for dma allocations
+ * @dma_io_tlb_mem: Internal for swiotlb io_tlb_mem override.
  * @archdata:        For arch-specific additions.
  * @of_node: Associated device tree node.
  * @fwnode:  Associated device node supplied by platform firmware.

@@ -521,6 +522,9 @@ struct device {
 #ifdef CONFIG_DMA_CMA
      struct cma *cma_area;           /* contiguous memory area for dma
                                         allocations */
+#endif
+#ifdef CONFIG_DMA_RESTRICTED_POOL
+     struct io_tlb_mem *dma_io_tlb_mem;
 #endif
      /* arch specific additions */
      struct dev_archdata     archdata;

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 216854a5e513..03ad6e3b4056 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h

@@ -72,7 +72,8 @@ extern enum swiotlb_force swiotlb_force;
  *           range check to see if the memory was in fact allocated by this
  *           API.
  * @nslabs:  The number of IO TLB blocks (in groups of 64) between @start and
- *           @end. This is command line adjustable via setup_io_tlb_npages.
+ *           @end. For default swiotlb, this is command line adjustable via
+ *           setup_io_tlb_npages.
  * @used:    The number of used IO TLB block.
  * @list:    The free list describing the number of free entries available
  *           from each index.

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index b849b01a446f..1d8eb4de0d01 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c

@@ -39,6 +39,13 @@
 #ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
 #endif
+#ifdef CONFIG_DMA_RESTRICTED_POOL
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/slab.h>
+#endif

 #include <asm/io.h>
 #include <asm/dma.h>

@@ -690,3 +697,72 @@ static int __init swiotlb_create_default_debugfs(void)
 late_initcall(swiotlb_create_default_debugfs);

 #endif
+
+#ifdef CONFIG_DMA_RESTRICTED_POOL
+static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
+                                 struct device *dev)
+{
+     struct io_tlb_mem *mem = rmem->priv;
+     unsigned long nslabs = rmem->size >> IO_TLB_SHIFT;
+
+     if (dev->dma_io_tlb_mem)
+             return 0;
+
+     /*
+      * Since multiple devices can share the same pool, the private data,
+      * io_tlb_mem struct, will be initialized by the first device attached
+      * to it.
+      */
+     if (!mem) {
+             mem = kzalloc(struct_size(mem, slots, nslabs), GFP_KERNEL);
+             if (!mem)
+                     return -ENOMEM;
+
+             if (PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
+                     kfree(mem);
+                     return -EINVAL;

This could probably deserve a warning here to indicate that the reserved
area must be accessible within the linear mapping as I would expect a
lot of people to trip over that.

Ok. Will add it.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
--
Florian