| Message ID | 20220913082448.31120-4-nicolinc@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iommu: Define EINVAL as device/domain incompatibility | expand |
On 9/13/2022 1:24 AM, Nicolin Chen wrote: > Cases like VFIO wish to attach a device to an existing domain that was > not allocated specifically from the device. This raises a condition > where the IOMMU driver can fail the domain attach because the domain and > device are incompatible with each other. > > This is a soft failure that can be resolved by using a different domain. > > Provide a dedicated errno EINVAL from the IOMMU driver during attach that > the reason attached failed is because of domain incompatability. > > VFIO can use this to know attach is a soft failure and it should continue > searching. Otherwise the attach will be a hard failure and VFIO will > return the code to userspace. > > Update kdocs first to add rules of return errno to ->attach_dev ops. > > Suggested-by: Jason Gunthorpe <jgg@nvidia.com> > Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> > --- > include/linux/iommu.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index ea30f00dc145..c5d7ec0187c7 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -266,6 +266,17 @@ struct iommu_ops { > /** > * struct iommu_domain_ops - domain specific operations > * @attach_dev: attach an iommu domain to a device > + * Rules of its return errno: > + * EINVAL - Exclusively, device and domain are incompatible. Must > + * avoid kernel prints along with this errno. Any EINVAL > + * returned from kAPIs must be converted to ENODEV if it > + * is device-specific, or to some other reasonable errno > + * being listed below > + * ENOMEM - Out of memory > + * ENOSPC - No space left on device > + * EBUSY - Device is attached to a domain and cannot be changed > + * ENODEV - Device specific errors, not able to be attached > + * <others> - Treated as ENODEV by the caller. Use is discouraged It is my understanding that kernel-doc won't preserve your formatting without extra directives. See the "Note" after <https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#return-values> > * @detach_dev: detach an iommu domain from a device > * @map: map a physically contiguous memory region to an iommu domain > * @map_pages: map a physically contiguous set of pages of the same size to
Hi Jeff, On Tue, Sep 13, 2022 at 11:41:35AM -0700, Jeff Johnson wrote: > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > > index ea30f00dc145..c5d7ec0187c7 100644 > > --- a/include/linux/iommu.h > > +++ b/include/linux/iommu.h > > @@ -266,6 +266,17 @@ struct iommu_ops { > > /** > > * struct iommu_domain_ops - domain specific operations > > * @attach_dev: attach an iommu domain to a device > > + * Rules of its return errno: > > + * EINVAL - Exclusively, device and domain are incompatible. Must > > + * avoid kernel prints along with this errno. Any EINVAL > > + * returned from kAPIs must be converted to ENODEV if it > > + * is device-specific, or to some other reasonable errno > > + * being listed below > > + * ENOMEM - Out of memory > > + * ENOSPC - No space left on device > > + * EBUSY - Device is attached to a domain and cannot be changed > > + * ENODEV - Device specific errors, not able to be attached > > + * <others> - Treated as ENODEV by the caller. Use is discouraged > > It is my understanding that kernel-doc won't preserve your formatting > without extra directives. See the "Note" after > <https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#return-values> Thanks for the review! Perhaps the following one would work: diff --git a/include/linux/iommu.h b/include/linux/iommu.h index ea30f00dc145..14f078b58e17 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -266,6 +266,17 @@ struct iommu_ops { /** * struct iommu_domain_ops - domain specific operations * @attach_dev: attach an iommu domain to a device + * Return: + * * 0 - success + * * EINVAL - Exclusively, device and domain are incompatible. Must avoid + * kernel prints along with this errno. Any EINVAL returned from + * a kAPI must be converted to ENODEV if it is device-specific, + * or to some other reasonable errno being listed below + * * ENOMEM - Out of memory + * * ENOSPC - No space left on device + * * EBUSY - Device is attached to a domain and cannot be changed + * * ENODEV - Device specific errors, not able to be attached + * * <others> - Treated as ENODEV by the caller. Use is discouraged * @detach_dev: detach an iommu domain from a device * @map: map a physically contiguous memory region to an iommu domain * @map_pages: map a physically contiguous set of pages of the same size to
diff --git a/include/linux/iommu.h b/include/linux/iommu.h index ea30f00dc145..c5d7ec0187c7 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -266,6 +266,17 @@ struct iommu_ops { /** * struct iommu_domain_ops - domain specific operations * @attach_dev: attach an iommu domain to a device + * Rules of its return errno: + * EINVAL - Exclusively, device and domain are incompatible. Must + * avoid kernel prints along with this errno. Any EINVAL + * returned from kAPIs must be converted to ENODEV if it + * is device-specific, or to some other reasonable errno + * being listed below + * ENOMEM - Out of memory + * ENOSPC - No space left on device + * EBUSY - Device is attached to a domain and cannot be changed + * ENODEV - Device specific errors, not able to be attached + * <others> - Treated as ENODEV by the caller. Use is discouraged * @detach_dev: detach an iommu domain from a device * @map: map a physically contiguous memory region to an iommu domain * @map_pages: map a physically contiguous set of pages of the same size to
Cases like VFIO wish to attach a device to an existing domain that was not allocated specifically from the device. This raises a condition where the IOMMU driver can fail the domain attach because the domain and device are incompatible with each other. This is a soft failure that can be resolved by using a different domain. Provide a dedicated errno EINVAL from the IOMMU driver during attach that the reason attached failed is because of domain incompatability. VFIO can use this to know attach is a soft failure and it should continue searching. Otherwise the attach will be a hard failure and VFIO will return the code to userspace. Update kdocs first to add rules of return errno to ->attach_dev ops. Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> --- include/linux/iommu.h | 11 +++++++++++ 1 file changed, 11 insertions(+)