Re: [PATCH 13/15] swiotlb: merge swiotlb-xen initialization into swiotlb

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 3/14/22 3:31 AM, Christoph Hellwig wrote:
> -
>   static void __init pci_xen_swiotlb_init(void)
>   {
>   	if (!xen_initial_domain() && !x86_swiotlb_enable)
>   		return;
>   	x86_swiotlb_enable = true;
> -	xen_swiotlb = true;
> -	xen_swiotlb_init_early();
> +	swiotlb_init_remap(true, x86_swiotlb_flags, xen_swiotlb_fixup);


I think we need to have SWIOTLB_ANY set in x86_swiotlb_flags here.



>   	dma_ops = &xen_swiotlb_dma_ops;
>   	if (IS_ENABLED(CONFIG_PCI))
>   		pci_request_acs();
> @@ -88,14 +85,16 @@ static void __init pci_xen_swiotlb_init(void)
>   
>   int pci_xen_swiotlb_init_late(void)
>   {
> -	int rc;
> -
> -	if (xen_swiotlb)
> +	if (dma_ops == &xen_swiotlb_dma_ops)
>   		return 0;
>   
> -	rc = xen_swiotlb_init();
> -	if (rc)
> -		return rc;
> +	/* we can work with the default swiotlb */
> +	if (!io_tlb_default_mem.nslabs) {
> +		int rc = swiotlb_init_late(swiotlb_size_or_default(),
> +					   GFP_KERNEL, xen_swiotlb_fixup);


This may be comment for previous patch but looking at swiotlb_init_late():


retry:
        order = get_order(nslabs << IO_TLB_SHIFT);
        nslabs = SLABS_PER_PAGE << order;
        bytes = nslabs << IO_TLB_SHIFT;

        while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
                vstart = (void *)__get_free_pages(gfp_mask | __GFP_NOWARN,
                                                  order);
                if (vstart)
                        break;
                order--;
        }

        if (!vstart)
                return -ENOMEM;
        if (remap)
                rc = remap(vstart, nslabs);
        if (rc) {
                free_pages((unsigned long)vstart, order);

                /* Min is 2MB */
                if (nslabs <= 1024)
                        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",
                        (PAGE_SIZE << order) >> 20);
                nslabs = SLABS_PER_PAGE << order; <=======
        }

        rc = swiotlb_late_init_with_tbl(vstart, nslabs);

Notice that we don't do remap() after final update to nslabs. We should.



-boris