Messages in this thread | | | Date | Tue, 23 Aug 2022 15:30:21 +0800 | Subject | Re: [PATCH v11 05/13] iommu: Add attach/detach_dev_pasid iommu interface | From | Baolu Lu <> |
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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
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