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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 09, 2022 at 05:00:16AM +0000, Tian, Kevin wrote: > > I have started this effort by combining this list and the one from > > the side thread: > > > > @@ -266,6 +266,13 @@ struct iommu_ops { > > /** > > * struct iommu_domain_ops - domain specific operations > > * @attach_dev: attach an iommu domain to a device > > + * Rules of its return errno: > > + * ENOMEM - Out of memory > > + * EINVAL - Device and domain are incompatible > > + * EBUSY - Device is attached to a domain and cannot be changed > > With this definition then probably @attach_dev should not return -EBUSY > at all given it's already checked in the start of __iommu_attach_group(): I think the EBUSY would be only for non-conforming drivers. The API semantic is you can always attach a new domain and replace an existing domain. So things like AMD's "can't do anything but idenitity on RID when PASID enabled" would be -EBUSY. Seems right that it should be rare though. > > + * ENODEV - Device or domain is messed up: device is not mapped > > + * to an IOMMU, no domain can attach, and etc. > > if domain is messed up then should return -EINVAL given using another domain > might just work. IMHO here -ENODEV should only cover device specific problems > preventing this device from being attached to by any domain. Agree > > + * - Same behavior as ENODEV, use is discouraged > > didn't get the "Same behavior" part. Does it suggest all other errnos should > be converted to ENODEV? It says all other errnos should be treated as ENODEV by the caller but forwarded to userspace for further detail. > btw what about -ENOSPC? It's sane to allocate some resource in the attach > path while the resource might be not available, e.g.: Seems resaonable that it is similar to ENOMEM > As discussed in a side thread a note might be added to exempt calling > kAPI outside of the iommu driver. Sadly, not really.. The driver is responsible to santize this if it is relevant. It is the main downside of this approach. Jason _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel