Re: [PATCH RFC 06/11] iommu/sva: Use attach/detach_pasid_dev in SVA interfaces

[Lu Baolu]

On 2022/3/21 19:33, Jean-Philippe Brucker wrote:
> On Sun, Mar 20, 2022 at 02:40:25PM +0800, Lu Baolu wrote:
> > diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
> > index 106506143896..47cf98e661ff 100644
> > --- a/drivers/iommu/iommu-sva-lib.c
> > +++ b/drivers/iommu/iommu-sva-lib.c
> > @@ -3,6 +3,8 @@
> >    * Helpers for IOMMU drivers implementing SVA
> >    */
> >   #include <linux/mutex.h>
> > +#include <linux/iommu.h>
> > +#include <linux/slab.h>
> >   #include <linux/sched/mm.h>
> >   
> >   #include "iommu-sva-lib.h"
> > @@ -69,3 +71,101 @@ struct mm_struct *iommu_sva_find(ioasid_t pasid)
> >   	return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
> >   }
> >   EXPORT_SYMBOL_GPL(iommu_sva_find);
> > +
> > +static struct iommu_domain *iommu_sva_domain_alloc(struct device *dev)
> > +{
> > +	struct bus_type *bus = dev->bus;
> > +	struct iommu_domain *domain;
> > +
> > +	if (!bus || !bus->iommu_ops)
> > +		return NULL;
> > +
> > +	domain = bus->iommu_ops->domain_alloc(IOMMU_DOMAIN_SVA);
> > +	if (domain)
> > +		domain->type = IOMMU_DOMAIN_SVA;
> > +
> > +	return domain;
> > +}
> > +
> > +/**
> > + * iommu_sva_bind_device() - Bind a process address space to a device
> > + * @dev: the device
> > + * @mm: the mm to bind, caller must hold a reference to it
> > + * @drvdata: opaque data pointer to pass to bind callback
> > + *
> > + * Create a bond between device and address space, allowing the device to access
> > + * the mm using the returned PASID. If a bond already exists between @device and
> > + * @mm, it is returned and an additional reference is taken.
> This is not true anymore, we return a different structure for each call.
>
> > Caller must call
> > + * iommu_sva_unbind_device() to release each reference.
> > + *
> > + * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
> > + * initialize the required SVA features.
> > + *
> > + * On error, returns an ERR_PTR value.
> > + */
> > +struct iommu_sva *
> > +iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
> > +{
> > +	int ret = -EINVAL;
> > +	struct iommu_sva *handle;
> > +	struct iommu_domain *domain;
> > +
> > +	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> > +	if (!handle)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	ret = iommu_sva_alloc_pasid(mm, 1, (1U << dev->iommu->pasid_bits) - 1);
> > +	if (ret)
> > +		goto out;
> > +
> > +	domain = iommu_sva_domain_alloc(dev);
> > +	if (!domain) {
> > +		ret = -ENOMEM;
> > +		goto out;
> > +	}
> > +	domain->sva_cookie = mm;
> > +
> > +	ret = iommu_attach_device_pasid(domain, dev, mm->pasid);
> > +	if (ret)
> > +		goto out_free_domain;
> > +
> > +	handle->dev = dev;
> > +	handle->domain = domain;
> > +	handle->pasid = mm->pasid;
> > +
> > +	return handle;
> > +
> > +out_free_domain:
> > +	iommu_domain_free(domain);
> > +out:
> > +	kfree(handle);
> > +
> > +	return ERR_PTR(ret);
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
> > +
> > +/**
> > + * iommu_sva_unbind_device() - Remove a bond created with iommu_sva_bind_device
> > + * @handle: the handle returned by iommu_sva_bind_device()
> > + *
> > + * Put reference to a bond between device and address space.
> Same here. But I'd prefer keeping the old behavior so device drivers don't
> have to keep track of {dev, mm} pairs themselves.

Okay. Thank you for pointing this out. Let me figure it out in the next
version.

Best regards,
baolu