Re: [PATCH RFC 7/9] iommu: Introduce map_sg() as an IOMMU op for IOMMU drivers

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi,

On 1/28/21 4:01 AM, Chuck Lever wrote:
> From: Isaac J. Manjarres <isaacm@codeaurora.org>
> 
> Add support for IOMMU drivers to have their own map_sg() callbacks.
> This completes the path for having iommu_map_sg() invoke an IOMMU
> driver's map_sg() callback, which can then invoke the io-pgtable
> map_sg() callback with the entire scatter-gather list, so that it
> can be processed entirely in the io-pgtable layer.
> 
> For IOMMU drivers that do not provide a callback, the default
> implementation of iterating through the scatter-gather list, while
> calling iommu_map() will be used.
> 
> Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
> Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> [ cel: adjusted new iotlb_sync_map call site ]
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>   drivers/iommu/iommu.c |   12 ++++++++++++
>   include/linux/iommu.h |    5 +++++
>   2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index ed879a4d7fac..bd7adbd0339b 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2551,6 +2551,18 @@ static size_t __iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
>   	unsigned int i = 0;
>   	int ret;
>   
> +	if (ops->map_sg) {
> +		ret = ops->map_sg(domain, iova, sg, nents, prot, gfp, &mapped);
> +
> +		if (ops->iotlb_sync_map)
> +			ops->iotlb_sync_map(domain, iova, mapped);
> +
> +		if (ret)
> +			goto out_err;
> +
> +		return mapped;
> +	}
> +
>   	while (i <= nents) {
>   		phys_addr_t s_phys = sg_phys(sg);
>   
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index cd5f35022a25..667edc7b034a 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -192,6 +192,8 @@ struct iommu_iotlb_gather {
>    * @attach_dev: attach device to an iommu domain
>    * @detach_dev: detach device from an iommu domain
>    * @map: map a physically contiguous memory region to an iommu domain
> + * @map_sg: map a scatter-gather list of physically contiguous chunks to
> + *          an iommu domain.
>    * @unmap: unmap a physically contiguous memory region from an iommu domain
>    * @flush_iotlb_all: Synchronously flush all hardware TLBs for this domain
>    * @iotlb_sync_map: Sync mappings created recently using @map to the hardware
> @@ -243,6 +245,9 @@ struct iommu_ops {
>   	void (*detach_dev)(struct iommu_domain *domain, struct device *dev);
>   	int (*map)(struct iommu_domain *domain, unsigned long iova,
>   		   phys_addr_t paddr, size_t size, int prot, gfp_t gfp);
> +	int (*map_sg)(struct iommu_domain *domain, unsigned long iova,
> +		      struct scatterlist *sg, unsigned int nents, int prot,
> +		      gfp_t gfp, size_t *mapped);

I might be oversensitive. But what if the vendor iommu driver uses iova
beyond the pre-allocated range? It's safer if we could pass an iova
length parameter as well, so that the iommu driver could do some sanity
check.

Best regards,
baolu

>   	size_t (*unmap)(struct iommu_domain *domain, unsigned long iova,
>   		     size_t size, struct iommu_iotlb_gather *iotlb_gather);
>   	void (*flush_iotlb_all)(struct iommu_domain *domain);
> 
> 
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