Re: [PATCH RFC] iommu/virtio: Use page size bitmap supported by endpoint

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

Hi Bharat,

Please add the IOMMU list on your next posting

On Mon, Mar 23, 2020 at 02:11:08PM +0530, Bharat Bhushan wrote:
> Different endpoint can support different page size, probe
> endpoint if it supports specific page size otherwise use
> global page sizes.
> 
> Signed-off-by: Bharat Bhushan <bbhushan2@marvell.com>
> ---
>  drivers/iommu/virtio-iommu.c      | 24 ++++++++++++++++++++----
>  include/uapi/linux/virtio_iommu.h |  6 ++++++
>  2 files changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index cce329d71fba..e69347ca4ee6 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -78,6 +78,7 @@ struct viommu_endpoint {
>  	struct viommu_dev		*viommu;
>  	struct viommu_domain		*vdomain;
>  	struct list_head		resv_regions;
> +	u64				pgsize_bitmap;
>  };
>  
>  struct viommu_request {
> @@ -415,6 +416,14 @@ static int viommu_replay_mappings(struct viommu_domain *vdomain)
>  	return ret;
>  }
>  
> +static int viommu_set_pgsize_bitmap(struct viommu_endpoint *vdev,
> +				    struct virtio_iommu_probe_pgsize_mask *mask)
> +
> +{
> +	vdev->pgsize_bitmap = mask->pgsize_bitmap;

We need to read this through le64_to_cpu(). Also check that the length of
the field provided by the device is >= sizeof(mask) (like
viommu_add_resv_mem() does)

> +	return 0;
> +}
> +
>  static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
>  			       struct virtio_iommu_probe_resv_mem *mem,
>  			       size_t len)
> @@ -494,11 +503,13 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
>  	while (type != VIRTIO_IOMMU_PROBE_T_NONE &&
>  	       cur < viommu->probe_size) {
>  		len = le16_to_cpu(prop->length) + sizeof(*prop);
> -
>  		switch (type) {
>  		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
>  			ret = viommu_add_resv_mem(vdev, (void *)prop, len);
>  			break;
> +		case VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK:
> +			ret = viommu_set_pgsize_bitmap(vdev, (void *)prop);
> +			break;
>  		default:
>  			dev_err(dev, "unknown viommu prop 0x%x\n", type);
>  		}
> @@ -607,16 +618,21 @@ static struct iommu_domain *viommu_domain_alloc(unsigned type)
>  	return &vdomain->domain;
>  }
>  
> -static int viommu_domain_finalise(struct viommu_dev *viommu,
> +static int viommu_domain_finalise(struct viommu_endpoint *vdev,
>  				  struct iommu_domain *domain)
>  {
>  	int ret;
>  	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +	struct viommu_dev *viommu = vdev->viommu;
>  
>  	vdomain->viommu		= viommu;
>  	vdomain->map_flags	= viommu->map_flags;
>  
> -	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
> +	if (vdev->pgsize_bitmap)
> +		domain->pgsize_bitmap = vdev->pgsize_bitmap;
> +	else
> +		domain->pgsize_bitmap	= viommu->pgsize_bitmap;
> +

nit: it could be nicer to initialize vdev->pgsize_bitmap in add_device(),
override it in probe_endpoint(), and just copy it here.

>  	domain->geometry	= viommu->geometry;
>  
>  	ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
> @@ -657,7 +673,7 @@ static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  		 * Properly initialize the domain now that we know which viommu
>  		 * owns it.
>  		 */
> -		ret = viommu_domain_finalise(vdev->viommu, domain);
> +		ret = viommu_domain_finalise(vdev, domain);

Attaching additional endpoints with different masks to the domain should
return an error

>  	} else if (vdomain->viommu != vdev->viommu) {
>  		dev_err(dev, "cannot attach to foreign vIOMMU\n");
>  		ret = -EXDEV;
> diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h
> index 237e36a280cb..aff3db0ef54b 100644
> --- a/include/uapi/linux/virtio_iommu.h
> +++ b/include/uapi/linux/virtio_iommu.h
> @@ -111,6 +111,7 @@ struct virtio_iommu_req_unmap {
>  
>  #define VIRTIO_IOMMU_PROBE_T_NONE		0
>  #define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
> +#define VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK	2
>  
>  #define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
>  
> @@ -119,6 +120,11 @@ struct virtio_iommu_probe_property {
>  	__le16					length;
>  };
>  
> +struct virtio_iommu_probe_pgsize_mask {
> +	struct virtio_iommu_probe_property	head;

Compilers will introduce 4 bytes of padding here, to align the next field.
We need to make them explicit by adding a 4-bytes 'reserved' field.

> +	uint64_t				pgsize_bitmap;

__le64

Thanks,
Jean

> +};
> +
>  #define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
>  #define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
>  
> -- 
> 2.17.1
>