[PATCH 12/15] swiotlb: provide swiotlb_init variants that remap the buffer

[Christoph Hellwig <hch@xxxxxx>]

To shared more code between swiotlb and xen-swiotlb, offer a
swiotlb_init_remap interface and add a remap callback to
swiotlb_init_late that will allow Xen to remap the buffer the
buffer without duplicating much of the logic.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 arch/x86/pci/sta2x11-fixup.c |  2 +-
 include/linux/swiotlb.h      |  5 ++++-
 kernel/dma/swiotlb.c         | 36 +++++++++++++++++++++++++++++++++---
 3 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/arch/x86/pci/sta2x11-fixup.c b/arch/x86/pci/sta2x11-fixup.c
index c7e6faf59a861..7368afc039987 100644
--- a/arch/x86/pci/sta2x11-fixup.c
+++ b/arch/x86/pci/sta2x11-fixup.c
@@ -57,7 +57,7 @@ static void sta2x11_new_instance(struct pci_dev *pdev)
                int size = STA2X11_SWIOTLB_SIZE;
                /* First instance: register your own swiotlb area */
                dev_info(&pdev->dev, "Using SWIOTLB (size %i)\n", size);
-               if (swiotlb_init_late(size, GFP_DMA))
+               if (swiotlb_init_late(size, GFP_DMA, NULL))
                        dev_emerg(&pdev->dev, "init swiotlb failed\n");
        }
        list_add(&instance->list, &sta2x11_instance_list);
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index ee655f2e4d28b..7b50c82f84ce9 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -36,8 +36,11 @@ struct scatterlist;
 
 int swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, unsigned int flags);
 unsigned long swiotlb_size_or_default(void);
+void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
+       int (*remap)(void *tlb, unsigned long nslabs));
+int swiotlb_init_late(size_t size, gfp_t gfp_mask,
+       int (*remap)(void *tlb, unsigned long nslabs));
 extern int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs);
-int swiotlb_init_late(size_t size, gfp_t gfp_mask);
 extern void __init swiotlb_update_mem_attributes(void);
 
 phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, phys_addr_t phys,
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 119187afc65ec..d5fe8f5e08300 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -256,9 +256,11 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long 
nslabs,
  * Statically reserve bounce buffer space and initialize bounce buffer data
  * structures for the software IO TLB used to implement the DMA API.
  */
-void __init swiotlb_init(bool addressing_limit, unsigned int flags)
+void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
+               int (*remap)(void *tlb, unsigned long nslabs))
 {
-       size_t bytes = PAGE_ALIGN(default_nslabs << IO_TLB_SHIFT);
+       unsigned long nslabs = default_nslabs;
+       size_t bytes;
        void *tlb;
 
        if (!addressing_limit && !swiotlb_force_bounce)
@@ -271,12 +273,23 @@ void __init swiotlb_init(bool addressing_limit, unsigned 
int flags)
         * allow to pick a location everywhere for hypervisors with guest
         * memory encryption.
         */
+retry:
+       bytes = PAGE_ALIGN(default_nslabs << IO_TLB_SHIFT);
        if (flags & SWIOTLB_ANY)
                tlb = memblock_alloc(bytes, PAGE_SIZE);
        else
                tlb = memblock_alloc_low(bytes, PAGE_SIZE);
        if (!tlb)
                goto fail;
+       if (remap && remap(tlb, nslabs) < 0) {
+               memblock_free(tlb, PAGE_ALIGN(bytes));
+
+               nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
+               if (nslabs < IO_TLB_MIN_SLABS)
+                       panic("%s: Failed to remap %zu bytes\n",
+                             __func__, bytes);
+               goto retry;
+       }
        if (swiotlb_init_with_tbl(tlb, default_nslabs, flags))
                goto fail_free_mem;
        return;
@@ -287,12 +300,18 @@ void __init swiotlb_init(bool addressing_limit, unsigned 
int flags)
        pr_warn("Cannot allocate buffer");
 }
 
+void __init swiotlb_init(bool addressing_limit, unsigned int flags)
+{
+       return swiotlb_init_remap(addressing_limit, flags, NULL);
+}
+
 /*
  * Systems with larger DMA zones (those that don't support ISA) can
  * initialize the swiotlb later using the slab allocator if needed.
  * This should be just like above, but with some error catching.
  */
-int swiotlb_init_late(size_t size, gfp_t gfp_mask)
+int swiotlb_init_late(size_t size, gfp_t gfp_mask,
+               int (*remap)(void *tlb, unsigned long nslabs))
 {
        unsigned long nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
        unsigned long bytes;
@@ -303,6 +322,7 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask)
        if (swiotlb_force_disable)
                return 0;
 
+retry:
        order = get_order(nslabs << IO_TLB_SHIFT);
        nslabs = SLABS_PER_PAGE << order;
        bytes = nslabs << IO_TLB_SHIFT;
@@ -323,6 +343,16 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask)
                        (PAGE_SIZE << order) >> 20);
                nslabs = SLABS_PER_PAGE << order;
        }
+       if (remap)
+               rc = remap(vstart, nslabs);
+       if (rc) {
+               free_pages((unsigned long)vstart, order);
+ 
+               nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
+               if (nslabs < IO_TLB_MIN_SLABS)
+                       return rc;
+               goto retry;
+       }
        rc = swiotlb_late_init_with_tbl(vstart, nslabs);
        if (rc)
                free_pages((unsigned long)vstart, order);
-- 
2.30.2