Re: [PATCH 2/4] iommu/virtio: Add probe request

[Robin Murphy <robin.murphy@arm.com>]

On 14/02/18 14:53, Jean-Philippe Brucker wrote:
> When the device offers the probe feature, send a probe request for each
> device managed by the IOMMU. Extract RESV_MEM information. When we
> encounter a MSI doorbell region, set it up as a IOMMU_RESV_MSI region.
> This will tell other subsystems that there is no need to map the MSI
> doorbell in the virtio-iommu, because MSIs bypass it.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> ---
>   drivers/iommu/virtio-iommu.c      | 163 ++++++++++++++++++++++++++++++++++++--
>   include/uapi/linux/virtio_iommu.h |  37 +++++++++
>   2 files changed, 193 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index a9c9245e8ba2..3ac4b38eaf19 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -45,6 +45,7 @@ struct viommu_dev {
>   	struct iommu_domain_geometry	geometry;
>   	u64				pgsize_bitmap;
>   	u8				domain_bits;
> +	u32				probe_size;
>   };
>   
>   struct viommu_mapping {
> @@ -72,6 +73,7 @@ struct viommu_domain {
>   struct viommu_endpoint {
>   	struct viommu_dev		*viommu;
>   	struct viommu_domain		*vdomain;
> +	struct list_head		resv_regions;
>   };
>   
>   struct viommu_request {
> @@ -140,6 +142,10 @@ static int viommu_get_req_size(struct viommu_dev *viommu,
>   	case VIRTIO_IOMMU_T_UNMAP:
>   		size = sizeof(r->unmap);
>   		break;
> +	case VIRTIO_IOMMU_T_PROBE:
> +		*bottom += viommu->probe_size;
> +		size = sizeof(r->probe) + *bottom;
> +		break;
>   	default:
>   		return -EINVAL;
>   	}
> @@ -448,6 +454,105 @@ static int viommu_replay_mappings(struct viommu_domain *vdomain)
>   	return ret;
>   }
>   
> +static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
> +			       struct virtio_iommu_probe_resv_mem *mem,
> +			       size_t len)
> +{
> +	struct iommu_resv_region *region = NULL;
> +	unsigned long prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
> +
> +	u64 addr = le64_to_cpu(mem->addr);
> +	u64 size = le64_to_cpu(mem->size);
> +
> +	if (len < sizeof(*mem))
> +		return -EINVAL;
> +
> +	switch (mem->subtype) {
> +	case VIRTIO_IOMMU_RESV_MEM_T_MSI:
> +		region = iommu_alloc_resv_region(addr, size, prot,
> +						 IOMMU_RESV_MSI);
> +		break;
> +	case VIRTIO_IOMMU_RESV_MEM_T_RESERVED:
> +	default:
> +		region = iommu_alloc_resv_region(addr, size, 0,
> +						 IOMMU_RESV_RESERVED);
> +		break;
> +	}
> +
> +	list_add(&vdev->resv_regions, &region->list);
> +
> +	/*
> +	 * Treat unknown subtype as RESERVED, but urge users to update their
> +	 * driver.
> +	 */
> +	if (mem->subtype != VIRTIO_IOMMU_RESV_MEM_T_RESERVED &&
> +	    mem->subtype != VIRTIO_IOMMU_RESV_MEM_T_MSI)
> +		pr_warn("unknown resv mem subtype 0x%x\n", mem->subtype);

Might as well avoid the extra comparisons by incorporating this into the 
switch statement, i.e.:

	default:
		dev_warn(vdev->viommu_dev->dev, ...);
		/* Fallthrough */
	case VIRTIO_IOMMU_RESV_MEM_T_RESERVED:
		...

(dev_warn is generally preferable to pr_warn when feasible)

> +
> +	return 0;
> +}
> +
> +static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
> +{
> +	int ret;
> +	u16 type, len;
> +	size_t cur = 0;
> +	struct virtio_iommu_req_probe *probe;
> +	struct virtio_iommu_probe_property *prop;
> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +	struct viommu_endpoint *vdev = fwspec->iommu_priv;
> +
> +	if (!fwspec->num_ids)
> +		/* Trouble ahead. */
> +		return -EINVAL;
> +
> +	probe = kzalloc(sizeof(*probe) + viommu->probe_size +
> +			sizeof(struct virtio_iommu_req_tail), GFP_KERNEL);
> +	if (!probe)
> +		return -ENOMEM;
> +
> +	probe->head.type = VIRTIO_IOMMU_T_PROBE;
> +	/*
> +	 * For now, assume that properties of an endpoint that outputs multiple
> +	 * IDs are consistent. Only probe the first one.
> +	 */
> +	probe->endpoint = cpu_to_le32(fwspec->ids[0]);
> +
> +	ret = viommu_send_req_sync(viommu, probe);
> +	if (ret)
> +		goto out_free;
> +
> +	prop = (void *)probe->properties;
> +	type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
> +
> +	while (type != VIRTIO_IOMMU_PROBE_T_NONE &&
> +	       cur < viommu->probe_size) {
> +		len = le16_to_cpu(prop->length);
> +
> +		switch (type) {
> +		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
> +			ret = viommu_add_resv_mem(vdev, (void *)prop->value, len);
> +			break;
> +		default:
> +			dev_dbg(dev, "unknown viommu prop 0x%x\n", type);
> +		}
> +
> +		if (ret)
> +			dev_err(dev, "failed to parse viommu prop 0x%x\n", type);
> +
> +		cur += sizeof(*prop) + len;
> +		if (cur >= viommu->probe_size)
> +			break;
> +
> +		prop = (void *)probe->properties + cur;
> +		type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
> +	}
> +
> +out_free:
> +	kfree(probe);
> +	return ret;
> +}
> +
>   /* IOMMU API */
>   
>   static bool viommu_capable(enum iommu_cap cap)
> @@ -703,6 +808,7 @@ static struct viommu_dev *viommu_get_by_fwnode(struct fwnode_handle *fwnode)
>   
>   static int viommu_add_device(struct device *dev)
>   {
> +	int ret;
>   	struct iommu_group *group;
>   	struct viommu_endpoint *vdev;
>   	struct viommu_dev *viommu = NULL;
> @@ -720,8 +826,16 @@ static int viommu_add_device(struct device *dev)
>   		return -ENOMEM;
>   
>   	vdev->viommu = viommu;
> +	INIT_LIST_HEAD(&vdev->resv_regions);
>   	fwspec->iommu_priv = vdev;
>   
> +	if (viommu->probe_size) {
> +		/* Get additional information for this endpoint */
> +		ret = viommu_probe_endpoint(viommu, dev);
> +		if (ret)
> +			return ret;
> +	}
> +
>   	/*
>   	 * Last step creates a default domain and attaches to it. Everything
>   	 * must be ready.
> @@ -735,7 +849,19 @@ static int viommu_add_device(struct device *dev)
>   
>   static void viommu_remove_device(struct device *dev)
>   {
> -	kfree(dev->iommu_fwspec->iommu_priv);
> +	struct viommu_endpoint *vdev;
> +	struct iommu_resv_region *entry, *next;
> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +
> +	if (!fwspec || fwspec->ops != &viommu_ops)
> +		return;

Oh good :) I guess that was just a patch-splitting issue. The group 
thing still applies, though.

Robin.

> +
> +	vdev = fwspec->iommu_priv;
> +
> +	list_for_each_entry_safe(entry, next, &vdev->resv_regions, list)
> +		kfree(entry);
> +
> +	kfree(vdev);
>   }
>   
>   static struct iommu_group *viommu_device_group(struct device *dev)
> @@ -753,15 +879,33 @@ static int viommu_of_xlate(struct device *dev, struct of_phandle_args *args)
>   
>   static void viommu_get_resv_regions(struct device *dev, struct list_head *head)
>   {
> -	struct iommu_resv_region *region;
> +	struct iommu_resv_region *entry, *new_entry, *msi = NULL;
> +	struct viommu_endpoint *vdev = dev->iommu_fwspec->iommu_priv;
>   	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
>   
> -	region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, prot,
> -					 IOMMU_RESV_SW_MSI);
> -	if (!region)
> -		return;
> +	list_for_each_entry(entry, &vdev->resv_regions, list) {
> +		/*
> +		 * If the device registered a bypass MSI windows, use it.
> +		 * Otherwise add a software-mapped region
> +		 */
> +		if (entry->type == IOMMU_RESV_MSI)
> +			msi = entry;
> +
> +		new_entry = kmemdup(entry, sizeof(*entry), GFP_KERNEL);
> +		if (!new_entry)
> +			return;
> +		list_add_tail(&new_entry->list, head);
> +	}
> +
> +	if (!msi) {
> +		msi = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH,
> +					      prot, IOMMU_RESV_SW_MSI);
> +		if (!msi)
> +			return;
> +
> +		list_add_tail(&msi->list, head);
> +	}
>   
> -	list_add_tail(&region->list, head);
>   	iommu_dma_get_resv_regions(dev, head);
>   }
>   
> @@ -852,6 +996,10 @@ static int viommu_probe(struct virtio_device *vdev)
>   			     struct virtio_iommu_config, domain_bits,
>   			     &viommu->domain_bits);
>   
> +	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_PROBE,
> +			     struct virtio_iommu_config, probe_size,
> +			     &viommu->probe_size);
> +
>   	viommu->geometry = (struct iommu_domain_geometry) {
>   		.aperture_start	= input_start,
>   		.aperture_end	= input_end,
> @@ -933,6 +1081,7 @@ static unsigned int features[] = {
>   	VIRTIO_IOMMU_F_MAP_UNMAP,
>   	VIRTIO_IOMMU_F_DOMAIN_BITS,
>   	VIRTIO_IOMMU_F_INPUT_RANGE,
> +	VIRTIO_IOMMU_F_PROBE,
>   };
>   
>   static struct virtio_device_id id_table[] = {
> diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h
> index 0de9b44db14d..2335d9ed4676 100644
> --- a/include/uapi/linux/virtio_iommu.h
> +++ b/include/uapi/linux/virtio_iommu.h
> @@ -15,6 +15,7 @@
>   #define VIRTIO_IOMMU_F_DOMAIN_BITS		1
>   #define VIRTIO_IOMMU_F_MAP_UNMAP		2
>   #define VIRTIO_IOMMU_F_BYPASS			3
> +#define VIRTIO_IOMMU_F_PROBE			4
>   
>   struct virtio_iommu_config {
>   	/* Supported page sizes */
> @@ -26,6 +27,9 @@ struct virtio_iommu_config {
>   	} input_range;
>   	/* Max domain ID size */
>   	__u8					domain_bits;
> +	__u8					padding[3];
> +	/* Probe buffer size */
> +	__u32					probe_size;
>   } __packed;
>   
>   /* Request types */
> @@ -33,6 +37,7 @@ struct virtio_iommu_config {
>   #define VIRTIO_IOMMU_T_DETACH			0x02
>   #define VIRTIO_IOMMU_T_MAP			0x03
>   #define VIRTIO_IOMMU_T_UNMAP			0x04
> +#define VIRTIO_IOMMU_T_PROBE			0x05
>   
>   /* Status types */
>   #define VIRTIO_IOMMU_S_OK			0x00
> @@ -104,6 +109,37 @@ struct virtio_iommu_req_unmap {
>   	struct virtio_iommu_req_tail		tail;
>   } __packed;
>   
> +#define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
> +#define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
> +
> +struct virtio_iommu_probe_resv_mem {
> +	__u8					subtype;
> +	__u8					reserved[3];
> +	__le64					addr;
> +	__le64					size;
> +} __packed;
> +
> +#define VIRTIO_IOMMU_PROBE_T_NONE		0
> +#define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
> +
> +#define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
> +
> +struct virtio_iommu_probe_property {
> +	__le16					type;
> +	__le16					length;
> +	__u8					value[];
> +} __packed;
> +
> +struct virtio_iommu_req_probe {
> +	struct virtio_iommu_req_head		head;
> +	__le32					endpoint;
> +	__u8					reserved[64];
> +
> +	__u8					properties[];
> +
> +	/* Tail follows the variable-length properties array (no padding) */
> +} __packed;
> +
>   union virtio_iommu_req {
>   	struct virtio_iommu_req_head		head;
>   
> @@ -111,6 +147,7 @@ union virtio_iommu_req {
>   	struct virtio_iommu_req_detach		detach;
>   	struct virtio_iommu_req_map		map;
>   	struct virtio_iommu_req_unmap		unmap;
> +	struct virtio_iommu_req_probe		probe;
>   };
>   
>   #endif
>