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Date:   Tue, 12 May 2020 10:53:39 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Bharat Bhushan <bbhushan2@marvell.com>
Cc:     jean-philippe@linaro.org, joro@8bytes.org, jasowang@redhat.com,
        virtualization@lists.linux-foundation.org,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        eric.auger.pro@gmail.com, eric.auger@redhat.com
Subject: Re: [PATCH v5] iommu/virtio: Use page size bitmap supported by
 endpoint
Message-ID: <20200512105149-mutt-send-email-mst@kernel.org>
References: <20200505093004.1935-1-bbhushan2@marvell.com>
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On Tue, May 05, 2020 at 03:00:04PM +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>
> ---
> v4->v5:
>  - Rebase to Linux v5.7-rc4
> 
> v3->v4:
>  - Fix whitespace error
> 
> v2->v3:
>  - Fixed error return for incompatible endpoint
>  - __u64 changed to __le64 in header file
> 
>  drivers/iommu/virtio-iommu.c      | 48 ++++++++++++++++++++++++++++---
>  include/uapi/linux/virtio_iommu.h |  7 +++++
>  2 files changed, 51 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index d5cac4f46ca5..9513d2ab819e 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 +416,19 @@ 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,
> +				    size_t len)
> +{
> +	u64 pgsize_bitmap = le64_to_cpu(mask->pgsize_bitmap);
> +
> +	if (len < sizeof(*mask))
> +		return -EINVAL;
> +
> +	vdev->pgsize_bitmap = pgsize_bitmap;
> +	return 0;
> +}
> +
>  static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
>  			       struct virtio_iommu_probe_resv_mem *mem,
>  			       size_t len)
> @@ -499,6 +513,9 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
>  		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, len);
> +			break;
>  		default:
>  			dev_err(dev, "unknown viommu prop 0x%x\n", type);
>  		}

So given this is necessary early in boot, how about we
add this in the config space? And maybe ACPI too ...


> @@ -630,7 +647,7 @@ static int viommu_domain_finalise(struct viommu_endpoint *vdev,
>  
>  	vdomain->id		= (unsigned int)ret;
>  
> -	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
> +	domain->pgsize_bitmap	= vdev->pgsize_bitmap;
>  	domain->geometry	= viommu->geometry;
>  
>  	vdomain->map_flags	= viommu->map_flags;
> @@ -654,6 +671,29 @@ static void viommu_domain_free(struct iommu_domain *domain)
>  	kfree(vdomain);
>  }
>  
> +/*
> + * Check whether the endpoint's capabilities are compatible with other
> + * endpoints in the domain. Report any inconsistency.
> + */
> +static bool viommu_endpoint_is_compatible(struct viommu_endpoint *vdev,
> +					  struct viommu_domain *vdomain)
> +{
> +	struct device *dev = vdev->dev;
> +
> +	if (vdomain->viommu != vdev->viommu) {
> +		dev_err(dev, "cannot attach to foreign vIOMMU\n");
> +		return false;
> +	}
> +
> +	if (vdomain->domain.pgsize_bitmap != vdev->pgsize_bitmap) {
> +		dev_err(dev, "incompatible domain bitmap 0x%lx != 0x%llx\n",
> +			vdomain->domain.pgsize_bitmap, vdev->pgsize_bitmap);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
>  static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  {
>  	int i;
> @@ -670,9 +710,8 @@ static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  		 * owns it.
>  		 */
>  		ret = viommu_domain_finalise(vdev, domain);
> -	} else if (vdomain->viommu != vdev->viommu) {
> -		dev_err(dev, "cannot attach to foreign vIOMMU\n");
> -		ret = -EXDEV;
> +	} else if (!viommu_endpoint_is_compatible(vdev, vdomain)) {
> +		ret = -EINVAL;
>  	}
>  	mutex_unlock(&vdomain->mutex);
>  
> @@ -886,6 +925,7 @@ static int viommu_add_device(struct device *dev)
>  
>  	vdev->dev = dev;
>  	vdev->viommu = viommu;
> +	vdev->pgsize_bitmap = viommu->pgsize_bitmap;
>  	INIT_LIST_HEAD(&vdev->resv_regions);
>  	dev_iommu_priv_set(dev, vdev);
>  
> diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h
> index 48e3c29223b5..2cced7accc99 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 +120,12 @@ struct virtio_iommu_probe_property {
>  	__le16					length;
>  };
>  
> +struct virtio_iommu_probe_pgsize_mask {
> +	struct virtio_iommu_probe_property	head;
> +	__u8					reserved[4];
> +	__le64					pgsize_bitmap;
> +};
> +
>  #define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
>  #define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
>  
> -- 
> 2.17.1