Re: [PATCH 01/10] swiotlb-xen: use vmalloc_to_page on vmalloc virt addresses

[Julien Grall]

Hi,

On 21/05/2020 00:45, Stefano Stabellini wrote:
> From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
>
> Don't just assume that virt_to_page works on all virtual addresses.
> Instead add a is_vmalloc_addr check and use vmalloc_to_page on vmalloc
> virt addresses.

Can you provide an example where swiotlb is used with vmalloc()?

> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> ---
>   drivers/xen/swiotlb-xen.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index b6d27762c6f8..a42129cba36e 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -335,6 +335,7 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>   	int order = get_order(size);
>   	phys_addr_t phys;
>   	u64 dma_mask = DMA_BIT_MASK(32);
> +	struct page *pg;
>   
>   	if (hwdev && hwdev->coherent_dma_mask)
>   		dma_mask = hwdev->coherent_dma_mask;
> @@ -346,9 +347,11 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>   	/* Convert the size to actually allocated. */
>   	size = 1UL << (order + XEN_PAGE_SHIFT);
>   
> +	pg = is_vmalloc_addr(vaddr) ? vmalloc_to_page(vaddr) :
> +				      virt_to_page(vaddr);

Common DMA code seems to protect this check with CONFIG_DMA_REMAP. Is it 
something we want to do it here as well? Or is there any other condition 
where vmalloc can happen?

>   	if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
>   		     range_straddles_page_boundary(phys, size)) &&
> -	    TestClearPageXenRemapped(virt_to_page(vaddr)))
> +	    TestClearPageXenRemapped(pg))
>   		xen_destroy_contiguous_region(phys, order);
>   
>   	xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);

Cheers,

--
Julien Grall