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

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 3/14/22 3:31 AM, Christoph Hellwig wrote:
> -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 +273,24 @@ 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));
> +
> +               /* Min is 2MB */
> +               if (nslabs <= 1024)

This is IO_TLB_MIN_SLABS, isn't it? (Xen code didn't say so but that's what it 
meant to say I believe)


> +                       panic("%s: Failed to remap %zu bytes\n",
> +                             __func__, bytes);
> +               nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
> +               goto retry;
> +       }
>
> @@ -303,6 +323,7 @@ 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;
> @@ -317,6 +338,17 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask)
>   
>   	if (!vstart)
>                 return -ENOMEM;
> +       if (remap)
> +               rc = remap(vstart, nslabs);
> +       if (rc) {
> +               free_pages((unsigned long)vstart, order);
> +
> +               /* Min is 2MB */
> +               if (nslabs <= 1024)

Same here.


-boris


> +                       return rc;
> +               nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
> +               goto retry;
> +       }
>   
>   	if (order != get_order(bytes)) {
>                 pr_warn("only able to allocate %ld MB\n",