Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
On 7/2/20 10:36 AM, Lu Baolu wrote: Hi Robin, On 7/1/20 8:18 PM, Robin Murphy wrote: On 2020-07-01 08:32, Lu Baolu wrote: Hi Robin, On 2020/7/1 0:51, Robin Murphy wrote: On 2020-06-30 02:03, Lu Baolu wrote: Hi Robin, On 6/29/20 7:56 PM, Robin Murphy wrote: On 2020-06-27 04:15, Lu Baolu wrote: The hardware assistant vfio mediated device is a use case of iommu aux-domain. The interactions between vfio/mdev and iommu during mdev creation and passthr are: - Create a group for mdev with iommu_group_alloc(); - Add the device to the group with group = iommu_group_alloc(); if (IS_ERR(group)) return PTR_ERR(group); ret = iommu_group_add_device(group, >dev); if (!ret) dev_info(>dev, "MDEV: group_id = %d\n", iommu_group_id(group)); - Allocate an aux-domain iommu_domain_alloc() - Attach the aux-domain to the physical device from which the mdev is created. iommu_aux_attach_device() In the whole process, an iommu group was allocated for the mdev and an iommu domain was attached to the group, but the group->domain leaves NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore. This adds iommu_group_get/set_domain() so that group->domain could be managed whenever a domain is attached or detached through the aux-domain api's. Letting external callers poke around directly in the internals of iommu_group doesn't look right to me. Unfortunately, it seems that the vifo iommu abstraction is deeply bound to the IOMMU subsystem. We can easily find other examples: iommu_group_get/set_iommudata() iommu_group_get/set_name() ... Sure, but those are ways for users of a group to attach useful information of their own to it, that doesn't matter to the IOMMU subsystem itself. The interface you've proposed gives callers rich new opportunities to fundamentally break correct operation of the API: dom = iommu_domain_alloc(); iommu_attach_group(dom, grp); ... iommu_group_set_domain(grp, NULL); // oops, leaked and can't ever detach properly now or perhaps: grp = iommu_group_alloc(); iommu_group_add_device(grp, dev); iommu_group_set_domain(grp, dom); ... iommu_detach_group(dom, grp); // oops, IOMMU driver might not handle this If a regular device is attached to one or more aux domains for PASID use, iommu_get_domain_for_dev() is still going to return the primary domain, so why should it be expected to behave differently for mediated Unlike the normal device attach, we will encounter two devices when it comes to aux-domain. - Parent physical device - this might be, for example, a PCIe device with PASID feature support, hence it is able to tag an unique PASID for DMA transfers originated from its subset. The device driver hence is able to wrapper this subset into an isolated: - Mediated device - a fake device created by the device driver mentioned above. Yes. All you mentioned are right for the parent device. But for mediated device, iommu_get_domain_for_dev() doesn't work even it has an valid iommu_group and iommu_domain. iommu_get_domain_for_dev() is a necessary interface for device drivers which want to support aux-domain. For example, Only if they want to follow this very specific notion of using made-up devices and groups to represent aux attachments. Even if a driver managing its own aux domains entirely privately does create child devices for them, it's not like it can't keep its domain pointers in drvdata if it wants to ;) Let's not conflate the current implementation of vfio_mdev with the general concepts involved here. struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); unsigned long pasid; domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; pasid = iommu_aux_get_pasid(domain, dev->parent); if (pasid == IOASID_INVALID) return -EINVAL; /* Program the device context with the PASID value */ Without this fix, iommu_get_domain_for_dev() always returns NULL and the device driver has no means to support aux-domain. So either the IOMMU API itself is missing the ability to do the right thing internally, or the mdev layer isn't using it appropriately. Either way, simply punching holes in the API for mdev to hack around its own mess doesn't seem like the best thing to do. The initial impression I got was that it's implicitly assumed here that the mdev itself is attached to exactly one aux domain and nothing else, at which point I would wonder why it's using aux at all, but are you saying that in fact no attach happens with the mdev group either way, only to the parent device? I'll admit I'm not hugely familiar with any of this, but it seems to me that the logical flow should be: - allocate domain - attach as aux to parent -
Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
Hi Robin, On 7/1/20 8:18 PM, Robin Murphy wrote: On 2020-07-01 08:32, Lu Baolu wrote: Hi Robin, On 2020/7/1 0:51, Robin Murphy wrote: On 2020-06-30 02:03, Lu Baolu wrote: Hi Robin, On 6/29/20 7:56 PM, Robin Murphy wrote: On 2020-06-27 04:15, Lu Baolu wrote: The hardware assistant vfio mediated device is a use case of iommu aux-domain. The interactions between vfio/mdev and iommu during mdev creation and passthr are: - Create a group for mdev with iommu_group_alloc(); - Add the device to the group with group = iommu_group_alloc(); if (IS_ERR(group)) return PTR_ERR(group); ret = iommu_group_add_device(group, >dev); if (!ret) dev_info(>dev, "MDEV: group_id = %d\n", iommu_group_id(group)); - Allocate an aux-domain iommu_domain_alloc() - Attach the aux-domain to the physical device from which the mdev is created. iommu_aux_attach_device() In the whole process, an iommu group was allocated for the mdev and an iommu domain was attached to the group, but the group->domain leaves NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore. This adds iommu_group_get/set_domain() so that group->domain could be managed whenever a domain is attached or detached through the aux-domain api's. Letting external callers poke around directly in the internals of iommu_group doesn't look right to me. Unfortunately, it seems that the vifo iommu abstraction is deeply bound to the IOMMU subsystem. We can easily find other examples: iommu_group_get/set_iommudata() iommu_group_get/set_name() ... Sure, but those are ways for users of a group to attach useful information of their own to it, that doesn't matter to the IOMMU subsystem itself. The interface you've proposed gives callers rich new opportunities to fundamentally break correct operation of the API: dom = iommu_domain_alloc(); iommu_attach_group(dom, grp); ... iommu_group_set_domain(grp, NULL); // oops, leaked and can't ever detach properly now or perhaps: grp = iommu_group_alloc(); iommu_group_add_device(grp, dev); iommu_group_set_domain(grp, dom); ... iommu_detach_group(dom, grp); // oops, IOMMU driver might not handle this If a regular device is attached to one or more aux domains for PASID use, iommu_get_domain_for_dev() is still going to return the primary domain, so why should it be expected to behave differently for mediated Unlike the normal device attach, we will encounter two devices when it comes to aux-domain. - Parent physical device - this might be, for example, a PCIe device with PASID feature support, hence it is able to tag an unique PASID for DMA transfers originated from its subset. The device driver hence is able to wrapper this subset into an isolated: - Mediated device - a fake device created by the device driver mentioned above. Yes. All you mentioned are right for the parent device. But for mediated device, iommu_get_domain_for_dev() doesn't work even it has an valid iommu_group and iommu_domain. iommu_get_domain_for_dev() is a necessary interface for device drivers which want to support aux-domain. For example, Only if they want to follow this very specific notion of using made-up devices and groups to represent aux attachments. Even if a driver managing its own aux domains entirely privately does create child devices for them, it's not like it can't keep its domain pointers in drvdata if it wants to ;) Let's not conflate the current implementation of vfio_mdev with the general concepts involved here. struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); unsigned long pasid; domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; pasid = iommu_aux_get_pasid(domain, dev->parent); if (pasid == IOASID_INVALID) return -EINVAL; /* Program the device context with the PASID value */ Without this fix, iommu_get_domain_for_dev() always returns NULL and the device driver has no means to support aux-domain. So either the IOMMU API itself is missing the ability to do the right thing internally, or the mdev layer isn't using it appropriately. Either way, simply punching holes in the API for mdev to hack around its own mess doesn't seem like the best thing to do. The initial impression I got was that it's implicitly assumed here that the mdev itself is attached to exactly one aux domain and nothing else, at which point I would wonder why it's using aux at all, but are you saying that in fact no attach happens with the mdev group either way, only to the parent device? I'll admit I'm not hugely familiar with any of this, but it seems to me that the logical flow should be: - allocate domain - attach as aux to parent - retrieve aux domain PASID - create mdev
Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
Hello, On 7/1/20 8:18 PM, Robin Murphy wrote: On 2020-07-01 08:32, Lu Baolu wrote: Hi Robin, On 2020/7/1 0:51, Robin Murphy wrote: On 2020-06-30 02:03, Lu Baolu wrote: Hi Robin, On 6/29/20 7:56 PM, Robin Murphy wrote: On 2020-06-27 04:15, Lu Baolu wrote: The hardware assistant vfio mediated device is a use case of iommu aux-domain. The interactions between vfio/mdev and iommu during mdev creation and passthr are: - Create a group for mdev with iommu_group_alloc(); - Add the device to the group with group = iommu_group_alloc(); if (IS_ERR(group)) return PTR_ERR(group); ret = iommu_group_add_device(group, >dev); if (!ret) dev_info(>dev, "MDEV: group_id = %d\n", iommu_group_id(group)); - Allocate an aux-domain iommu_domain_alloc() - Attach the aux-domain to the physical device from which the mdev is created. iommu_aux_attach_device() In the whole process, an iommu group was allocated for the mdev and an iommu domain was attached to the group, but the group->domain leaves NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore. This adds iommu_group_get/set_domain() so that group->domain could be managed whenever a domain is attached or detached through the aux-domain api's. Letting external callers poke around directly in the internals of iommu_group doesn't look right to me. Unfortunately, it seems that the vifo iommu abstraction is deeply bound to the IOMMU subsystem. We can easily find other examples: iommu_group_get/set_iommudata() iommu_group_get/set_name() ... Sure, but those are ways for users of a group to attach useful information of their own to it, that doesn't matter to the IOMMU subsystem itself. The interface you've proposed gives callers rich new opportunities to fundamentally break correct operation of the API: dom = iommu_domain_alloc(); iommu_attach_group(dom, grp); ... iommu_group_set_domain(grp, NULL); // oops, leaked and can't ever detach properly now or perhaps: grp = iommu_group_alloc(); iommu_group_add_device(grp, dev); iommu_group_set_domain(grp, dom); ... iommu_detach_group(dom, grp); // oops, IOMMU driver might not handle this If a regular device is attached to one or more aux domains for PASID use, iommu_get_domain_for_dev() is still going to return the primary domain, so why should it be expected to behave differently for mediated Unlike the normal device attach, we will encounter two devices when it comes to aux-domain. - Parent physical device - this might be, for example, a PCIe device with PASID feature support, hence it is able to tag an unique PASID for DMA transfers originated from its subset. The device driver hence is able to wrapper this subset into an isolated: - Mediated device - a fake device created by the device driver mentioned above. Yes. All you mentioned are right for the parent device. But for mediated device, iommu_get_domain_for_dev() doesn't work even it has an valid iommu_group and iommu_domain. iommu_get_domain_for_dev() is a necessary interface for device drivers which want to support aux-domain. For example, Only if they want to follow this very specific notion of using made-up devices and groups to represent aux attachments. Even if a driver managing its own aux domains entirely privately does create child devices for them, it's not like it can't keep its domain pointers in drvdata if it wants to ;) Let's not conflate the current implementation of vfio_mdev with the general concepts involved here. struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); unsigned long pasid; domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; pasid = iommu_aux_get_pasid(domain, dev->parent); if (pasid == IOASID_INVALID) return -EINVAL; /* Program the device context with the PASID value */ Without this fix, iommu_get_domain_for_dev() always returns NULL and the device driver has no means to support aux-domain. So either the IOMMU API itself is missing the ability to do the right thing internally, or the mdev layer isn't using it appropriately. Either way, simply punching holes in the API for mdev to hack around its own mess doesn't seem like the best thing to do. The initial impression I got was that it's implicitly assumed here that the mdev itself is attached to exactly one aux domain and nothing else, at which point I would wonder why it's using aux at all, but are you saying that in fact no attach happens with the mdev group either way, only to the parent device? I'll admit I'm not hugely familiar with any of this, but it seems to me that the logical flow should be: - allocate domain - attach as aux to parent - retrieve aux domain PASID - create mdev
Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
On 2020-07-01 08:32, Lu Baolu wrote: Hi Robin, On 2020/7/1 0:51, Robin Murphy wrote: On 2020-06-30 02:03, Lu Baolu wrote: Hi Robin, On 6/29/20 7:56 PM, Robin Murphy wrote: On 2020-06-27 04:15, Lu Baolu wrote: The hardware assistant vfio mediated device is a use case of iommu aux-domain. The interactions between vfio/mdev and iommu during mdev creation and passthr are: - Create a group for mdev with iommu_group_alloc(); - Add the device to the group with group = iommu_group_alloc(); if (IS_ERR(group)) return PTR_ERR(group); ret = iommu_group_add_device(group, >dev); if (!ret) dev_info(>dev, "MDEV: group_id = %d\n", iommu_group_id(group)); - Allocate an aux-domain iommu_domain_alloc() - Attach the aux-domain to the physical device from which the mdev is created. iommu_aux_attach_device() In the whole process, an iommu group was allocated for the mdev and an iommu domain was attached to the group, but the group->domain leaves NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore. This adds iommu_group_get/set_domain() so that group->domain could be managed whenever a domain is attached or detached through the aux-domain api's. Letting external callers poke around directly in the internals of iommu_group doesn't look right to me. Unfortunately, it seems that the vifo iommu abstraction is deeply bound to the IOMMU subsystem. We can easily find other examples: iommu_group_get/set_iommudata() iommu_group_get/set_name() ... Sure, but those are ways for users of a group to attach useful information of their own to it, that doesn't matter to the IOMMU subsystem itself. The interface you've proposed gives callers rich new opportunities to fundamentally break correct operation of the API: dom = iommu_domain_alloc(); iommu_attach_group(dom, grp); ... iommu_group_set_domain(grp, NULL); // oops, leaked and can't ever detach properly now or perhaps: grp = iommu_group_alloc(); iommu_group_add_device(grp, dev); iommu_group_set_domain(grp, dom); ... iommu_detach_group(dom, grp); // oops, IOMMU driver might not handle this If a regular device is attached to one or more aux domains for PASID use, iommu_get_domain_for_dev() is still going to return the primary domain, so why should it be expected to behave differently for mediated Unlike the normal device attach, we will encounter two devices when it comes to aux-domain. - Parent physical device - this might be, for example, a PCIe device with PASID feature support, hence it is able to tag an unique PASID for DMA transfers originated from its subset. The device driver hence is able to wrapper this subset into an isolated: - Mediated device - a fake device created by the device driver mentioned above. Yes. All you mentioned are right for the parent device. But for mediated device, iommu_get_domain_for_dev() doesn't work even it has an valid iommu_group and iommu_domain. iommu_get_domain_for_dev() is a necessary interface for device drivers which want to support aux-domain. For example, Only if they want to follow this very specific notion of using made-up devices and groups to represent aux attachments. Even if a driver managing its own aux domains entirely privately does create child devices for them, it's not like it can't keep its domain pointers in drvdata if it wants to ;) Let's not conflate the current implementation of vfio_mdev with the general concepts involved here. struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); unsigned long pasid; domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; pasid = iommu_aux_get_pasid(domain, dev->parent); if (pasid == IOASID_INVALID) return -EINVAL; /* Program the device context with the PASID value */ Without this fix, iommu_get_domain_for_dev() always returns NULL and the device driver has no means to support aux-domain. So either the IOMMU API itself is missing the ability to do the right thing internally, or the mdev layer isn't using it appropriately. Either way, simply punching holes in the API for mdev to hack around its own mess doesn't seem like the best thing to do. The initial impression I got was that it's implicitly assumed here that the mdev itself is attached to exactly one aux domain and nothing else, at which point I would wonder why it's using aux at all, but are you saying that in fact no attach happens with the mdev group either way, only to the parent device? I'll admit I'm not hugely familiar with any of this, but it seems to me that the logical flow should be: - allocate domain - attach as aux to parent - retrieve aux domain PASID - create mdev child based on PASID - attach mdev to domain (normally)
Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
Hi Robin, On 2020/7/1 0:51, Robin Murphy wrote: On 2020-06-30 02:03, Lu Baolu wrote: Hi Robin, On 6/29/20 7:56 PM, Robin Murphy wrote: On 2020-06-27 04:15, Lu Baolu wrote: The hardware assistant vfio mediated device is a use case of iommu aux-domain. The interactions between vfio/mdev and iommu during mdev creation and passthr are: - Create a group for mdev with iommu_group_alloc(); - Add the device to the group with group = iommu_group_alloc(); if (IS_ERR(group)) return PTR_ERR(group); ret = iommu_group_add_device(group, >dev); if (!ret) dev_info(>dev, "MDEV: group_id = %d\n", iommu_group_id(group)); - Allocate an aux-domain iommu_domain_alloc() - Attach the aux-domain to the physical device from which the mdev is created. iommu_aux_attach_device() In the whole process, an iommu group was allocated for the mdev and an iommu domain was attached to the group, but the group->domain leaves NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore. This adds iommu_group_get/set_domain() so that group->domain could be managed whenever a domain is attached or detached through the aux-domain api's. Letting external callers poke around directly in the internals of iommu_group doesn't look right to me. Unfortunately, it seems that the vifo iommu abstraction is deeply bound to the IOMMU subsystem. We can easily find other examples: iommu_group_get/set_iommudata() iommu_group_get/set_name() ... Sure, but those are ways for users of a group to attach useful information of their own to it, that doesn't matter to the IOMMU subsystem itself. The interface you've proposed gives callers rich new opportunities to fundamentally break correct operation of the API: dom = iommu_domain_alloc(); iommu_attach_group(dom, grp); ... iommu_group_set_domain(grp, NULL); // oops, leaked and can't ever detach properly now or perhaps: grp = iommu_group_alloc(); iommu_group_add_device(grp, dev); iommu_group_set_domain(grp, dom); ... iommu_detach_group(dom, grp); // oops, IOMMU driver might not handle this If a regular device is attached to one or more aux domains for PASID use, iommu_get_domain_for_dev() is still going to return the primary domain, so why should it be expected to behave differently for mediated Unlike the normal device attach, we will encounter two devices when it comes to aux-domain. - Parent physical device - this might be, for example, a PCIe device with PASID feature support, hence it is able to tag an unique PASID for DMA transfers originated from its subset. The device driver hence is able to wrapper this subset into an isolated: - Mediated device - a fake device created by the device driver mentioned above. Yes. All you mentioned are right for the parent device. But for mediated device, iommu_get_domain_for_dev() doesn't work even it has an valid iommu_group and iommu_domain. iommu_get_domain_for_dev() is a necessary interface for device drivers which want to support aux-domain. For example, Only if they want to follow this very specific notion of using made-up devices and groups to represent aux attachments. Even if a driver managing its own aux domains entirely privately does create child devices for them, it's not like it can't keep its domain pointers in drvdata if it wants to ;) Let's not conflate the current implementation of vfio_mdev with the general concepts involved here. struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); unsigned long pasid; domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; pasid = iommu_aux_get_pasid(domain, dev->parent); if (pasid == IOASID_INVALID) return -EINVAL; /* Program the device context with the PASID value */ Without this fix, iommu_get_domain_for_dev() always returns NULL and the device driver has no means to support aux-domain. So either the IOMMU API itself is missing the ability to do the right thing internally, or the mdev layer isn't using it appropriately. Either way, simply punching holes in the API for mdev to hack around its own mess doesn't seem like the best thing to do. The initial impression I got was that it's implicitly assumed here that the mdev itself is attached to exactly one aux domain and nothing else, at which point I would wonder why it's using aux at all, but are you saying that in fact no attach happens with the mdev group either way, only to the parent device? I'll admit I'm not hugely familiar with any of this, but it seems to me that the logical flow should be: - allocate domain - attach as aux to parent - retrieve aux domain PASID - create mdev child based on PASID - attach mdev to domain (normally) Of course that might require giving
Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
On 2020-06-30 02:03, Lu Baolu wrote: Hi Robin, On 6/29/20 7:56 PM, Robin Murphy wrote: On 2020-06-27 04:15, Lu Baolu wrote: The hardware assistant vfio mediated device is a use case of iommu aux-domain. The interactions between vfio/mdev and iommu during mdev creation and passthr are: - Create a group for mdev with iommu_group_alloc(); - Add the device to the group with group = iommu_group_alloc(); if (IS_ERR(group)) return PTR_ERR(group); ret = iommu_group_add_device(group, >dev); if (!ret) dev_info(>dev, "MDEV: group_id = %d\n", iommu_group_id(group)); - Allocate an aux-domain iommu_domain_alloc() - Attach the aux-domain to the physical device from which the mdev is created. iommu_aux_attach_device() In the whole process, an iommu group was allocated for the mdev and an iommu domain was attached to the group, but the group->domain leaves NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore. This adds iommu_group_get/set_domain() so that group->domain could be managed whenever a domain is attached or detached through the aux-domain api's. Letting external callers poke around directly in the internals of iommu_group doesn't look right to me. Unfortunately, it seems that the vifo iommu abstraction is deeply bound to the IOMMU subsystem. We can easily find other examples: iommu_group_get/set_iommudata() iommu_group_get/set_name() ... Sure, but those are ways for users of a group to attach useful information of their own to it, that doesn't matter to the IOMMU subsystem itself. The interface you've proposed gives callers rich new opportunities to fundamentally break correct operation of the API: dom = iommu_domain_alloc(); iommu_attach_group(dom, grp); ... iommu_group_set_domain(grp, NULL); // oops, leaked and can't ever detach properly now or perhaps: grp = iommu_group_alloc(); iommu_group_add_device(grp, dev); iommu_group_set_domain(grp, dom); ... iommu_detach_group(dom, grp); // oops, IOMMU driver might not handle this If a regular device is attached to one or more aux domains for PASID use, iommu_get_domain_for_dev() is still going to return the primary domain, so why should it be expected to behave differently for mediated Unlike the normal device attach, we will encounter two devices when it comes to aux-domain. - Parent physical device - this might be, for example, a PCIe device with PASID feature support, hence it is able to tag an unique PASID for DMA transfers originated from its subset. The device driver hence is able to wrapper this subset into an isolated: - Mediated device - a fake device created by the device driver mentioned above. Yes. All you mentioned are right for the parent device. But for mediated device, iommu_get_domain_for_dev() doesn't work even it has an valid iommu_group and iommu_domain. iommu_get_domain_for_dev() is a necessary interface for device drivers which want to support aux-domain. For example, Only if they want to follow this very specific notion of using made-up devices and groups to represent aux attachments. Even if a driver managing its own aux domains entirely privately does create child devices for them, it's not like it can't keep its domain pointers in drvdata if it wants to ;) Let's not conflate the current implementation of vfio_mdev with the general concepts involved here. struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); unsigned long pasid; domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; pasid = iommu_aux_get_pasid(domain, dev->parent); if (pasid == IOASID_INVALID) return -EINVAL; /* Program the device context with the PASID value */ Without this fix, iommu_get_domain_for_dev() always returns NULL and the device driver has no means to support aux-domain. So either the IOMMU API itself is missing the ability to do the right thing internally, or the mdev layer isn't using it appropriately. Either way, simply punching holes in the API for mdev to hack around its own mess doesn't seem like the best thing to do. The initial impression I got was that it's implicitly assumed here that the mdev itself is attached to exactly one aux domain and nothing else, at which point I would wonder why it's using aux at all, but are you saying that in fact no attach happens with the mdev group either way, only to the parent device? I'll admit I'm not hugely familiar with any of this, but it seems to me that the logical flow should be: - allocate domain - attach as aux to parent - retrieve aux domain PASID - create mdev child based on PASID - attach mdev to domain (normally) Of course that might require giving the
Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
Hi Robin, On 6/29/20 7:56 PM, Robin Murphy wrote: On 2020-06-27 04:15, Lu Baolu wrote: The hardware assistant vfio mediated device is a use case of iommu aux-domain. The interactions between vfio/mdev and iommu during mdev creation and passthr are: - Create a group for mdev with iommu_group_alloc(); - Add the device to the group with group = iommu_group_alloc(); if (IS_ERR(group)) return PTR_ERR(group); ret = iommu_group_add_device(group, >dev); if (!ret) dev_info(>dev, "MDEV: group_id = %d\n", iommu_group_id(group)); - Allocate an aux-domain iommu_domain_alloc() - Attach the aux-domain to the physical device from which the mdev is created. iommu_aux_attach_device() In the whole process, an iommu group was allocated for the mdev and an iommu domain was attached to the group, but the group->domain leaves NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore. This adds iommu_group_get/set_domain() so that group->domain could be managed whenever a domain is attached or detached through the aux-domain api's. Letting external callers poke around directly in the internals of iommu_group doesn't look right to me. Unfortunately, it seems that the vifo iommu abstraction is deeply bound to the IOMMU subsystem. We can easily find other examples: iommu_group_get/set_iommudata() iommu_group_get/set_name() ... If a regular device is attached to one or more aux domains for PASID use, iommu_get_domain_for_dev() is still going to return the primary domain, so why should it be expected to behave differently for mediated Unlike the normal device attach, we will encounter two devices when it comes to aux-domain. - Parent physical device - this might be, for example, a PCIe device with PASID feature support, hence it is able to tag an unique PASID for DMA transfers originated from its subset. The device driver hence is able to wrapper this subset into an isolated: - Mediated device - a fake device created by the device driver mentioned above. Yes. All you mentioned are right for the parent device. But for mediated device, iommu_get_domain_for_dev() doesn't work even it has an valid iommu_group and iommu_domain. iommu_get_domain_for_dev() is a necessary interface for device drivers which want to support aux-domain. For example, struct iommu_domain *domain; struct device *dev = mdev_dev(mdev); unsigned long pasid; domain = iommu_get_domain_for_dev(dev); if (!domain) return -ENODEV; pasid = iommu_aux_get_pasid(domain, dev->parent); if (pasid == IOASID_INVALID) return -EINVAL; /* Program the device context with the PASID value */ Without this fix, iommu_get_domain_for_dev() always returns NULL and the device driver has no means to support aux-domain. Best regards, baolu devices? AFAICS it's perfectly legitimate to have no primary domain if traffic-without-PASID is invalid. Robin. ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH 1/2] iommu: Add iommu_group_get/set_domain()
On 2020-06-27 04:15, Lu Baolu wrote:
The hardware assistant vfio mediated device is a use case of iommu
aux-domain. The interactions between vfio/mdev and iommu during mdev
creation and passthr are:
- Create a group for mdev with iommu_group_alloc();
- Add the device to the group with
group = iommu_group_alloc();
if (IS_ERR(group))
return PTR_ERR(group);
ret = iommu_group_add_device(group, >dev);
if (!ret)
dev_info(>dev, "MDEV: group_id = %d\n",
iommu_group_id(group));
- Allocate an aux-domain
iommu_domain_alloc()
- Attach the aux-domain to the physical device from which the mdev is
created.
iommu_aux_attach_device()
In the whole process, an iommu group was allocated for the mdev and an
iommu domain was attached to the group, but the group->domain leaves
NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore.
This adds iommu_group_get/set_domain() so that group->domain could be
managed whenever a domain is attached or detached through the aux-domain
api's.
Letting external callers poke around directly in the internals of
iommu_group doesn't look right to me.
If a regular device is attached to one or more aux domains for PASID
use, iommu_get_domain_for_dev() is still going to return the primary
domain, so why should it be expected to behave differently for mediated
devices? AFAICS it's perfectly legitimate to have no primary domain if
traffic-without-PASID is invalid.
Robin.
Fixes: 7bd50f0cd2fd5 ("vfio/type1: Add domain at(de)taching group helpers")
Signed-off-by: Lu Baolu
---
drivers/iommu/iommu.c | 28
include/linux/iommu.h | 14 ++
2 files changed, 42 insertions(+)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d43120eb1dc5..e2b665303d70 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -715,6 +715,34 @@ int iommu_group_set_name(struct iommu_group *group, const
char *name)
}
EXPORT_SYMBOL_GPL(iommu_group_set_name);
+/**
+ * iommu_group_get_domain - get domain of a group
+ * @group: the group
+ *
+ * This is called to get the domain of a group.
+ */
+struct iommu_domain *iommu_group_get_domain(struct iommu_group *group)
+{
+ return group->domain;
+}
+EXPORT_SYMBOL_GPL(iommu_group_get_domain);
+
+/**
+ * iommu_group_set_domain - set domain for a group
+ * @group: the group
+ * @domain: iommu domain
+ *
+ * This is called to set the domain for a group. In aux-domain case, a domain
+ * might attach or detach to an iommu group through the aux-domain apis, but
+ * the group->domain doesn't get a chance to be updated there.
+ */
+void iommu_group_set_domain(struct iommu_group *group,
+ struct iommu_domain *domain)
+{
+ group->domain = domain;
+}
+EXPORT_SYMBOL_GPL(iommu_group_set_domain);
+
static int iommu_create_device_direct_mappings(struct iommu_group *group,
struct device *dev)
{
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 5f0b7859d2eb..ff88d548a870 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -496,6 +496,9 @@ extern void iommu_group_set_iommudata(struct iommu_group
*group,
void *iommu_data,
void (*release)(void *iommu_data));
extern int iommu_group_set_name(struct iommu_group *group, const char *name);
+extern struct iommu_domain *iommu_group_get_domain(struct iommu_group *group);
+extern void iommu_group_set_domain(struct iommu_group *group,
+ struct iommu_domain *domain);
extern int iommu_group_add_device(struct iommu_group *group,
struct device *dev);
extern void iommu_group_remove_device(struct device *dev);
@@ -840,6 +843,17 @@ static inline int iommu_group_set_name(struct iommu_group
*group,
return -ENODEV;
}
+static inline
+struct iommu_domain *iommu_group_get_domain(struct iommu_group *group)
+{
+ return NULL;
+}
+
+static inline void iommu_group_set_domain(struct iommu_group *group,
+ struct iommu_domain *domain)
+{
+}
+
static inline int iommu_group_add_device(struct iommu_group *group,
struct device *dev)
{
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[PATCH 1/2] iommu: Add iommu_group_get/set_domain()
The hardware assistant vfio mediated device is a use case of iommu
aux-domain. The interactions between vfio/mdev and iommu during mdev
creation and passthr are:
- Create a group for mdev with iommu_group_alloc();
- Add the device to the group with
group = iommu_group_alloc();
if (IS_ERR(group))
return PTR_ERR(group);
ret = iommu_group_add_device(group, >dev);
if (!ret)
dev_info(>dev, "MDEV: group_id = %d\n",
iommu_group_id(group));
- Allocate an aux-domain
iommu_domain_alloc()
- Attach the aux-domain to the physical device from which the mdev is
created.
iommu_aux_attach_device()
In the whole process, an iommu group was allocated for the mdev and an
iommu domain was attached to the group, but the group->domain leaves
NULL. As the result, iommu_get_domain_for_dev() doesn't work anymore.
This adds iommu_group_get/set_domain() so that group->domain could be
managed whenever a domain is attached or detached through the aux-domain
api's.
Fixes: 7bd50f0cd2fd5 ("vfio/type1: Add domain at(de)taching group helpers")
Signed-off-by: Lu Baolu
---
drivers/iommu/iommu.c | 28
include/linux/iommu.h | 14 ++
2 files changed, 42 insertions(+)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d43120eb1dc5..e2b665303d70 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -715,6 +715,34 @@ int iommu_group_set_name(struct iommu_group *group, const
char *name)
}
EXPORT_SYMBOL_GPL(iommu_group_set_name);
+/**
+ * iommu_group_get_domain - get domain of a group
+ * @group: the group
+ *
+ * This is called to get the domain of a group.
+ */
+struct iommu_domain *iommu_group_get_domain(struct iommu_group *group)
+{
+ return group->domain;
+}
+EXPORT_SYMBOL_GPL(iommu_group_get_domain);
+
+/**
+ * iommu_group_set_domain - set domain for a group
+ * @group: the group
+ * @domain: iommu domain
+ *
+ * This is called to set the domain for a group. In aux-domain case, a domain
+ * might attach or detach to an iommu group through the aux-domain apis, but
+ * the group->domain doesn't get a chance to be updated there.
+ */
+void iommu_group_set_domain(struct iommu_group *group,
+ struct iommu_domain *domain)
+{
+ group->domain = domain;
+}
+EXPORT_SYMBOL_GPL(iommu_group_set_domain);
+
static int iommu_create_device_direct_mappings(struct iommu_group *group,
struct device *dev)
{
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 5f0b7859d2eb..ff88d548a870 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -496,6 +496,9 @@ extern void iommu_group_set_iommudata(struct iommu_group
*group,
void *iommu_data,
void (*release)(void *iommu_data));
extern int iommu_group_set_name(struct iommu_group *group, const char *name);
+extern struct iommu_domain *iommu_group_get_domain(struct iommu_group *group);
+extern void iommu_group_set_domain(struct iommu_group *group,
+ struct iommu_domain *domain);
extern int iommu_group_add_device(struct iommu_group *group,
struct device *dev);
extern void iommu_group_remove_device(struct device *dev);
@@ -840,6 +843,17 @@ static inline int iommu_group_set_name(struct iommu_group
*group,
return -ENODEV;
}
+static inline
+struct iommu_domain *iommu_group_get_domain(struct iommu_group *group)
+{
+ return NULL;
+}
+
+static inline void iommu_group_set_domain(struct iommu_group *group,
+ struct iommu_domain *domain)
+{
+}
+
static inline int iommu_group_add_device(struct iommu_group *group,
struct device *dev)
{
--
2.17.1
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