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

Christoph Hellwig
2022-04-04T05:07:37Z

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@lst.de>
---
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