| Message ID | 8c3dbf153b63a3002a46bab6e707c63fd8635bb8.1663744983.git.nicolinc@nvidia.com |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | Define EINVAL as device/domain incompatibility | expand |
On 9/21/22 4:23 PM, 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 why the attach failed is because of domain incompatibility. > > VFIO can use this to know that the 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 to add rules of return value to the attach_dev op and APIs. > > Suggested-by: Jason Gunthorpe<jgg@nvidia.com> > Signed-off-by: Nicolin Chen<nicolinc@nvidia.com> > --- > drivers/iommu/iommu.c | 22 ++++++++++++++++++++++ > include/linux/iommu.h | 12 ++++++++++++ > 2 files changed, 34 insertions(+) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 3a808146b50f..1d1e32aeaae6 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -1975,6 +1975,17 @@ static int __iommu_attach_device(struct iommu_domain *domain, > return ret; > } > > +/** > + * iommu_attach_device - Attach a device to an IOMMU domain Normally we say "attach an iommu domain to a device/group ...". Best regards, baolu
On Thu, Sep 22, 2022 at 10:02:42AM +0800, Baolu Lu wrote: > > +/** > > + * iommu_attach_device - Attach a device to an IOMMU domain > > Normally we say "attach an iommu domain to a device/group ...". OK. I can fix it in the next respin. And I'll add your Reviewed-by in the other two patches too. Thanks! Nic
> From: Nicolin Chen <nicolinc@nvidia.com> > Sent: Wednesday, September 21, 2022 4:23 PM > > > +/** > + * iommu_attach_device - Attach a device to an IOMMU domain > + * @domain: IOMMU domain to attach > + * @dev: Device that will be attached > + * > + * Returns 0 on success and error code on failure > + * > + * Note that EINVAL may be returned as a soft failure if the domain and > device > + * are incompatible due to some previous configuration of the domain, in > which > + * case attaching the same device to a different domain may succeed. Revise a bit: * Note that EINVAL can be treated as a soft failure, indicating * that certain configuration of the domain is incompatible with * the device. In this case attaching a different domain to the * device may succeed. Apart from that: Reviewed-by: Kevin Tian <kevin.tian@intel.com>
On Thu, Sep 22, 2022 at 08:17:03AM +0000, Tian, Kevin wrote: > External email: Use caution opening links or attachments > > > > From: Nicolin Chen <nicolinc@nvidia.com> > > Sent: Wednesday, September 21, 2022 4:23 PM > > > > > > +/** > > + * iommu_attach_device - Attach a device to an IOMMU domain > > + * @domain: IOMMU domain to attach > > + * @dev: Device that will be attached > > + * > > + * Returns 0 on success and error code on failure > > + * > > + * Note that EINVAL may be returned as a soft failure if the domain and > > device > > + * are incompatible due to some previous configuration of the domain, in > > which > > + * case attaching the same device to a different domain may succeed. > > Revise a bit: > > * Note that EINVAL can be treated as a soft failure, indicating > * that certain configuration of the domain is incompatible with > * the device. In this case attaching a different domain to the > * device may succeed. Done. And added all your "Reviewed-by" too. Thanks!
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 3a808146b50f..1d1e32aeaae6 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -1975,6 +1975,17 @@ static int __iommu_attach_device(struct iommu_domain *domain, return ret; } +/** + * iommu_attach_device - Attach a device to an IOMMU domain + * @domain: IOMMU domain to attach + * @dev: Device that will be attached + * + * Returns 0 on success and error code on failure + * + * Note that EINVAL may be returned as a soft failure if the domain and device + * are incompatible due to some previous configuration of the domain, in which + * case attaching the same device to a different domain may succeed. + */ int iommu_attach_device(struct iommu_domain *domain, struct device *dev) { struct iommu_group *group; @@ -2101,6 +2112,17 @@ static int __iommu_attach_group(struct iommu_domain *domain, return ret; } +/** + * iommu_attach_group - Attach an IOMMU group to an IOMMU domain + * @domain: IOMMU domain to attach + * @group: IOMMU group that will be attached + * + * Returns 0 on success and error code on failure + * + * Note that EINVAL may be returned as a soft failure if the domain and group + * are incompatible due to some previous configuration of the domain, in which + * case attaching the same group to a different domain may succeed. + */ int iommu_attach_group(struct iommu_domain *domain, struct iommu_group *group) { int ret; diff --git a/include/linux/iommu.h b/include/linux/iommu.h index ea30f00dc145..13a33b04e867 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -266,6 +266,18 @@ struct iommu_ops { /** * struct iommu_domain_ops - domain specific operations * @attach_dev: attach an iommu domain to a device + * Return: + * * 0 - success + * * EINVAL - can indicate that device and domain are incompatible due to + * some previous configuration of the domain, in which case the + * driver shouldn't log an error, since it is legitimate for a + * caller to test reuse of existing domains. Otherwise, it may + * still represent some other fundamental problem + * * ENOMEM - out of memory + * * ENOSPC - non-ENOMEM type of resource allocation failures + * * 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 why the attach failed is because of domain incompatibility. VFIO can use this to know that the 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 to add rules of return value to the attach_dev op and APIs. Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> --- drivers/iommu/iommu.c | 22 ++++++++++++++++++++++ include/linux/iommu.h | 12 ++++++++++++ 2 files changed, 34 insertions(+)