Hi,
On Mon, Nov 26, 2018 at 07:29:45AM +0000, Tian, Kevin wrote:
> btw Baolu just reminded me one thing which is worthy of noting here.
> 'primary' vs. 'aux' concept makes sense only when we look from a device
> p.o.v. That binding relationship is not (*should not be*) carry-and-forwarded
> cross devices. every domain must be explicitly attached to other devices
> (instead of implicitly attached being above example), and new primary/aux
> attribute on another device will be decided at attach time.
Okay, so after all the discussions we had I learned a few more things
about the scalable mode feature and thought a bit longer about how to
best support it in the IOMMU-API.
The concept of sub-domains I initially proposed certainly makes no
sense, but scalable-mode specific attach/detach functions do. So instead
of a sub-domain mode, I'd like to propose device-feature sets.
The posted patch-set already includes this as device-attributes, but I
don't like this naming as we are really talking about additional
feature sets of a device. So how about we introduce this:
enum iommu_dev_features {
/* ... */
IOMMU_DEV_FEAT_AUX,
IOMMU_DEV_FEAT_SVA,
/* ... */
};
/* Check if a device supports a given feature of the IOMMU-API */
bool iommu_dev_has_feature(struct device *dev, enum iommu_dev_features
*feat);
/*
* Only works if iommu_dev_has_feature(dev, IOMMU_DEV_FEAT_AUX)
* returns true
*
* Also, as long as domains are attached to a device through
* this interface, any trys to call iommu_attach_device() should
* fail (iommu_detach_device() can't fail, so we fail on the
* tryint to re-attach). This should make us safe against a
* device being attached to a guest as a whole while there are
* still pasid users on it (aux and sva).
*/
int iommu_aux_attach_device(struct iommu_domain *domain,
struct device *dev);
int iommu_aux_detach_device(struct iommu_domain *domain,
struct device *dev);
/*
* I know we are targeting a system-wide pasid-space, so that
* the pasid would be the same for one domain on all devices,
* let's just keep the option open to have different
* pasid-spaces in one system. Also this way we can use it to
* check whether the domain is attached to this device at all.
*
* returns pasid or <0 if domain has no pasid on that device.
*/
int iommu_aux_get_pasid(struct iommu_domain *domain,
struct device *dev);
/* So we need a iommu_aux_detach_all()? */
This concept can also be easily extended for supporting SVA in parallel
on the same device, with the same constraints regarding the behavior of
iommu_attach_device()/iommu_detach_device().
So what do you think about that approach?
Regards,
Joerg
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