Re: [PATCH 6/6] x86/xen: open code alloc_vm_area in arch_gnttab_valloc

[boris . ostrovsky]

On 9/18/20 12:37 PM, Christoph Hellwig wrote:
>  
> +static int gnttab_apply(pte_t *pte, unsigned long addr, void *data)
> +{
> +	pte_t ***p = data;
> +
> +	**p = pte;
> +	(*p)++;
> +	return 0;
> +}
> +
>  static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
>  {
>  	area->ptes = kmalloc_array(nr_frames, sizeof(*area->ptes), GFP_KERNEL);
>  	if (area->ptes == NULL)
>  		return -ENOMEM;
> -
> -	area->area = alloc_vm_area(PAGE_SIZE * nr_frames, area->ptes);
> -	if (area->area == NULL) {
> -		kfree(area->ptes);
> -		return -ENOMEM;
> -	}
> -
> +	area->area = get_vm_area(PAGE_SIZE * nr_frames, VM_IOREMAP);
> +	if (!area->area)
> +		goto out_free_ptes;
> +	if (apply_to_page_range(&init_mm, (unsigned long)area->area->addr,
> +			PAGE_SIZE * nr_frames, gnttab_apply, &area->ptes))


This will end up incrementing area->ptes pointer. So perhaps something like


pte_t **ptes = area->ptes;

if (apply_to_page_range(&init_mm, (unsigned long)area->area->addr,
                        PAGE_SIZE * nr_frames, gnttab_apply, &ptes)) {

       ...

}


-boris