linux-kernel - Re: [PATCH RFC v1 02/11] iommu/virtio: Maintain a list of endpoints served by viommu

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Message-ID: <814df96d-8796-44f6-d5e5-09f36862c497@arm.com>
Date:   Thu, 30 Sep 2021 14:47:54 +0530
From:   Vivek Kumar Gautam <vivek.gautam@....com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org,
        virtualization@...ts.linux-foundation.org, joro@...tes.org,
        will.deacon@....com, mst@...hat.com, robin.murphy@....com,
        eric.auger@...hat.com, kevin.tian@...el.com,
        jacob.jun.pan@...ux.intel.com, yi.l.liu@...el.com,
        Lorenzo.Pieralisi@....com, shameerali.kolothum.thodi@...wei.com
Subject: Re: [PATCH RFC v1 02/11] iommu/virtio: Maintain a list of endpoints
 served by viommu_dev



On 9/21/21 9:29 PM, Jean-Philippe Brucker wrote:
> On Fri, Apr 23, 2021 at 03:21:38PM +0530, Vivek Gautam wrote:
>> Keeping a record of list of endpoints that are served by the virtio-iommu
>> device would help in redirecting the requests of page faults to the
>> correct endpoint device to handle such requests.
>>
>> Signed-off-by: Vivek Gautam <vivek.gautam@....com>
>> ---
>>   drivers/iommu/virtio-iommu.c | 21 +++++++++++++++++++++
>>   1 file changed, 21 insertions(+)
>>
>> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
>> index 50039070e2aa..c970f386f031 100644
>> --- a/drivers/iommu/virtio-iommu.c
>> +++ b/drivers/iommu/virtio-iommu.c
>> @@ -48,6 +48,7 @@ struct viommu_dev {
>>   	spinlock_t			request_lock;
>>   	struct list_head		requests;
>>   	void				*evts;
>> +	struct list_head		endpoints;
> 
> As we're going to search by ID, an xarray or rb_tree would be more
> appropriate than a list

Sure, I will update this with a rb_tree.

> 
>>   
>>   	/* Device configuration */
>>   	struct iommu_domain_geometry	geometry;
>> @@ -115,6 +116,12 @@ struct viommu_endpoint {
>>   	void				*pgtf;
>>   };
>>   
>> +struct viommu_ep_entry {
>> +	u32				eid;
>> +	struct viommu_endpoint		*vdev;
>> +	struct list_head		list;
>> +};
> 
> No need for a separate struct, I think you can just add the list head and
> id into viommu_endpoint.

Yea right. I will update it.

> 
>> +
>>   struct viommu_request {
>>   	struct list_head		list;
>>   	void				*writeback;
>> @@ -573,6 +580,7 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
>>   	size_t probe_len;
>>   	struct virtio_iommu_req_probe *probe;
>>   	struct virtio_iommu_probe_property *prop;
>> +	struct viommu_ep_entry *ep;
>>   	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>>   	struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);
>>   
>> @@ -640,6 +648,18 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
>>   		prop = (void *)probe->properties + cur;
>>   		type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
>>   	}
>> +	if (ret)
>> +		goto out_free;
>> +
>> +	ep = kzalloc(sizeof(*ep), GFP_KERNEL);
>> +	if (!ep) {
>> +		ret = -ENOMEM;
>> +		goto out_free;
>> +	}
>> +	ep->eid = probe->endpoint;
>> +	ep->vdev = vdev;
>> +
>> +	list_add(&ep->list, &viommu->endpoints);
> 
> This should be in viommu_probe_device() (viommu_probe_endpoint() is only
> called if F_PROBE is negotiated). I think we need a lock for this
> list/xarray

Sure, will fix this, and add the needed locking around.

Thanks & regards
Vivek

> 
> Thanks,
> Jean
> 
>>   
>>   out_free:
>>   	kfree(probe);
>> @@ -1649,6 +1669,7 @@ static int viommu_probe(struct virtio_device *vdev)
>>   	viommu->dev = dev;
>>   	viommu->vdev = vdev;
>>   	INIT_LIST_HEAD(&viommu->requests);
>> +	INIT_LIST_HEAD(&viommu->endpoints);
>>   
>>   	ret = viommu_init_vqs(viommu);
>>   	if (ret)
>> -- 
>> 2.17.1
>>