Re: [PATCH v6 03/33] xhci: sideband: add initial api to register a sideband entity

[Hillf Danton <hdanton@sina.com>]

On Fri, 15 Sep 2023 17:09:56 -0700 Wesley Cheng <quic_wcheng@quicinc.com>
> +static int
> +xhci_ring_to_sgtable(struct xhci_sideband *sb, struct xhci_ring *ring, struct device *dev)
> +{
> +	struct sg_table	*sgt;
> +	struct xhci_segment *seg;
> +	struct page **pages;
> +	unsigned int n_pages;
> +	size_t sz;
> +	int i;
> +
> +	sz = ring->num_segs * TRB_SEGMENT_SIZE;
> +	n_pages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> +	pages = kvmalloc_array(n_pages, sizeof(struct page *), GFP_KERNEL);
> +	if (!pages)
> +		return 0;
> +
> +	sgt = kzalloc(sizeof(struct sg_table), GFP_KERNEL);
> +	if (!sgt) {
> +		kvfree(pages);
> +		return 0;
> +	}
> +
> +	seg = ring->first_seg;
> +
> +	/*
> +	 * Rings can potentially have multiple segments, create an array that
> +	 * carries page references to allocated segments.  Utilize the
> +	 * sg_alloc_table_from_pages() to create the sg table, and to ensure
> +	 * that page links are created.
> +	 */
> +	for (i = 0; i < ring->num_segs; i++) {
> +		pages[i] = vmalloc_to_page(seg->trbs);
> +		seg = seg->next;
> +	}

Given dma_pool_zalloc() in xhci_segment_alloc() and dma_alloc_coherent() in
pool_alloc_page(), it is incorrect to get page from the cpu address returned
by the dma alloc routine.