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

Dongli Zhang
2022-04-04T07:09:08Z

On 4/3/22 10:05 PM, Christoph Hellwig wrote:
> 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);
> +

"warning: 1 line adds whitespace errors." above when I was applying the patch
for test.

Dongli Zhang

> + 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);
>