lkml.org 
[lkml]   [2022]   [Aug]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v11 05/13] iommu: Add attach/detach_dev_pasid iommu interface
From
On 2022/8/18 21:33, Jason Gunthorpe wrote:
> On Wed, Aug 17, 2022 at 09:20:16AM +0800, Lu Baolu wrote:
>
>> +static int __iommu_set_group_pasid(struct iommu_domain *domain,
>> + struct iommu_group *group, ioasid_t pasid)
>> +{
>> + struct iommu_domain *ops_domain;
>> + struct group_device *device;
>> + int ret = 0;
>> +
>> + if (domain == group->blocking_domain)
>> + ops_domain = xa_load(&group->pasid_array, pasid);
>> + else
>> + ops_domain = domain;
>
> This seems weird, why isn't this just always
>
> domain->ops->set_dev_pasid()?

Sure. I will fix this in the next version.

>
>> + if (curr) {
>> + ret = xa_err(curr) ? : -EBUSY;
>> + goto out_unlock;
>> + }
>> +
>> + ret = __iommu_set_group_pasid(domain, group, pasid);
>> + if (ret) {
>> + __iommu_set_group_pasid(group->blocking_domain, group, pasid);
>> + xa_erase(&group->pasid_array, pasid);
>
> I was looking at this trying to figure out why we are having
> attach/detach semantics vs set and this error handling seems to be the
> reason
>
> Lets add a comment because it is subtle thing:
>
> Setting a PASID to a blocking domain cannot fail, so we can always
> safely error unwind a failure to attach a domain back to the original
> group configuration of the PASID being unused.

Updated.

>
>> +/*
>> + * iommu_detach_device_pasid() - Detach the domain from pasid of device
>> + * @domain: the iommu domain.
>> + * @dev: the attached device.
>> + * @pasid: the pasid of the device.
>> + *
>> + * The @domain must have been attached to @pasid of the @dev with
>> + * iommu_attach_device_pasid().
>> + */
>> +void iommu_detach_device_pasid(struct iommu_domain *domain, struct device *dev,
>> + ioasid_t pasid)
>
> Don't pass domain here?

It is checked in the function to make sure that the detached domain is
the same one as the previous attached one.

>
>> +/*
>> + * iommu_get_domain_for_dev_pasid() - Retrieve domain for @pasid of @dev
>> + * @dev: the queried device
>> + * @pasid: the pasid of the device
>> + *
>> + * This is a variant of iommu_get_domain_for_dev(). It returns the existing
>> + * domain attached to pasid of a device. It's only for internal use of the
>> + * IOMMU subsystem. The caller must take care to avoid any possible
>> + * use-after-free case.
>
> How exactly does the caller manage that?

"... the returned domain pointer could only be used before detaching
from the device PASID."

>
>> + *
>> + * Return: attached domain on success, NULL otherwise.
>> + */
>> +struct iommu_domain *
>> +iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid)
>> +{
>> + struct iommu_domain *domain;
>> + struct iommu_group *group;
>> +
>> + if (!pasid_valid(pasid))
>> + return NULL;
>
> Why bother? If the pasid is not valid then it definitely won't be in the xarray.

Removed.

> But otherwise this overall thing seems fine to me

Thank you!

Best regards,
baolu

\
 
 \ /
  Last update: 2022-08-23 09:31    [W:0.295 / U:0.288 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site