Re: [PATCH v2 4/5] iommu/virtio: Pass end address to viommu_add_mapping()

[Eric Auger]

On 11/23/21 4:53 PM, Jean-Philippe Brucker wrote:
> To support identity mappings, the virtio-iommu driver must be able to
> represent full 64-bit ranges internally. Pass (start, end) instead of
> (start, size) to viommu_add/del_mapping().
>
> Clean comments. The one about the returned size was never true: when
> sweeping the whole address space the returned size will most certainly
> be smaller than 2^64.
>
> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>

Eric

> ---
>  drivers/iommu/virtio-iommu.c | 31 +++++++++++++++----------------
>  1 file changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index d63ec4d11b00..eceb9281c8c1 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -311,8 +311,8 @@ static int viommu_send_req_sync(struct viommu_dev *viommu, void *buf,
>   *
>   * On success, return the new mapping. Otherwise return NULL.
>   */
> -static int viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
> -			      phys_addr_t paddr, size_t size, u32 flags)
> +static int viommu_add_mapping(struct viommu_domain *vdomain, u64 iova, u64 end,
> +			      phys_addr_t paddr, u32 flags)
>  {
>  	unsigned long irqflags;
>  	struct viommu_mapping *mapping;
> @@ -323,7 +323,7 @@ static int viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
>  
>  	mapping->paddr		= paddr;
>  	mapping->iova.start	= iova;
> -	mapping->iova.last	= iova + size - 1;
> +	mapping->iova.last	= end;
>  	mapping->flags		= flags;
>  
>  	spin_lock_irqsave(&vdomain->mappings_lock, irqflags);
> @@ -338,26 +338,24 @@ static int viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
>   *
>   * @vdomain: the domain
>   * @iova: start of the range
> - * @size: size of the range. A size of 0 corresponds to the entire address
> - *	space.
> + * @end: end of the range
>   *
> - * On success, returns the number of unmapped bytes (>= size)
> + * On success, returns the number of unmapped bytes
>   */
>  static size_t viommu_del_mappings(struct viommu_domain *vdomain,
> -				  unsigned long iova, size_t size)
> +				  u64 iova, u64 end)
>  {
>  	size_t unmapped = 0;
>  	unsigned long flags;
> -	unsigned long last = iova + size - 1;
>  	struct viommu_mapping *mapping = NULL;
>  	struct interval_tree_node *node, *next;
>  
>  	spin_lock_irqsave(&vdomain->mappings_lock, flags);
> -	next = interval_tree_iter_first(&vdomain->mappings, iova, last);
> +	next = interval_tree_iter_first(&vdomain->mappings, iova, end);
>  	while (next) {
>  		node = next;
>  		mapping = container_of(node, struct viommu_mapping, iova);
> -		next = interval_tree_iter_next(node, iova, last);
> +		next = interval_tree_iter_next(node, iova, end);
>  
>  		/* Trying to split a mapping? */
>  		if (mapping->iova.start < iova)
> @@ -656,8 +654,8 @@ static void viommu_domain_free(struct iommu_domain *domain)
>  {
>  	struct viommu_domain *vdomain = to_viommu_domain(domain);
>  
> -	/* Free all remaining mappings (size 2^64) */
> -	viommu_del_mappings(vdomain, 0, 0);
> +	/* Free all remaining mappings */
> +	viommu_del_mappings(vdomain, 0, ULLONG_MAX);
>  
>  	if (vdomain->viommu)
>  		ida_free(&vdomain->viommu->domain_ids, vdomain->id);
> @@ -742,6 +740,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
>  {
>  	int ret;
>  	u32 flags;
> +	u64 end = iova + size - 1;
>  	struct virtio_iommu_req_map map;
>  	struct viommu_domain *vdomain = to_viommu_domain(domain);
>  
> @@ -752,7 +751,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
>  	if (flags & ~vdomain->map_flags)
>  		return -EINVAL;
>  
> -	ret = viommu_add_mapping(vdomain, iova, paddr, size, flags);
> +	ret = viommu_add_mapping(vdomain, iova, end, paddr, flags);
>  	if (ret)
>  		return ret;
>  
> @@ -761,7 +760,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
>  		.domain		= cpu_to_le32(vdomain->id),
>  		.virt_start	= cpu_to_le64(iova),
>  		.phys_start	= cpu_to_le64(paddr),
> -		.virt_end	= cpu_to_le64(iova + size - 1),
> +		.virt_end	= cpu_to_le64(end),
>  		.flags		= cpu_to_le32(flags),
>  	};
>  
> @@ -770,7 +769,7 @@ static int viommu_map(struct iommu_domain *domain, unsigned long iova,
>  
>  	ret = viommu_send_req_sync(vdomain->viommu, &map, sizeof(map));
>  	if (ret)
> -		viommu_del_mappings(vdomain, iova, size);
> +		viommu_del_mappings(vdomain, iova, end);
>  
>  	return ret;
>  }
> @@ -783,7 +782,7 @@ static size_t viommu_unmap(struct iommu_domain *domain, unsigned long iova,
>  	struct virtio_iommu_req_unmap unmap;
>  	struct viommu_domain *vdomain = to_viommu_domain(domain);
>  
> -	unmapped = viommu_del_mappings(vdomain, iova, size);
> +	unmapped = viommu_del_mappings(vdomain, iova, iova + size - 1);
>  	if (unmapped < size)
>  		return 0;
>