Re: [PATCH v4 05/12] vfio/iommufd: Introduce auto domain creation

[Joao Martins <joao.m.martins@oracle.com>]

On 16/07/2024 17:04, Eric Auger wrote:
> Hi Joao,
> 
> On 7/12/24 13:46, Joao Martins wrote:
>> There's generally two modes of operation for IOMMUFD:
>>
>> * The simple user API which intends to perform relatively simple things
>> with IOMMUs e.g. DPDK. It generally creates an IOAS and attach to VFIO
> 
> It generally creates? can you explicit what is "it"
> 
'It' here refers to the process/API-user

> I am confused by this automatic terminology again (not your fault). the doc says:
> "
> 
>   *
> 
>     Automatic domain - refers to an iommu domain created automatically
>     when attaching a device to an IOAS object. This is compatible to the
>     semantics of VFIO type1.
> 
>   *
> 
>     Manual domain - refers to an iommu domain designated by the user as
>     the target pagetable to be attached to by a device. Though currently
>     there are no uAPIs to directly create such domain, the datastructure
>     and algorithms are ready for handling that use case.
> 
> "
> 
> 
> in 1) the device is attached to the ioas id (using the auto domain if I am not wrong)
> Here you attach to an hwpt id. Isn't it a manual domain?
>

Correct.

The 'auto domains' generally refers to the kernel-equivalent own automatic
attaching to a new pagetable.

Here I call 'auto domains' in the userspace version too because we are doing the
exact same but from userspace, using the manual API in IOMMUFD.

>> and mainly performs IOAS_MAP and UNMAP.
>>
>> * The native IOMMUFD API where you have fine grained control of the
>> IOMMU domain and model it accordingly. This is where most new feature
>> are being steered to.
>>
>> For dirty tracking 2) is required, as it needs to ensure that
>> the stage-2/parent IOMMU domain will only attach devices
>> that support dirty tracking (so far it is all homogeneous in x86, likely
>> not the case for smmuv3). Such invariant on dirty tracking provides a
>> useful guarantee to VMMs that will refuse incompatible device
>> attachments for IOMMU domains.
>>
>> Dirty tracking insurance is enforced via HWPT_ALLOC, which is
>> responsible for creating an IOMMU domain. This is contrast to the
>> 'simple API' where the IOMMU domain is created by IOMMUFD automatically
>> when it attaches to VFIO (usually referred as autodomains) but it has
>> the needed handling for mdevs.
>>
>> To support dirty tracking with the advanced IOMMUFD API, it needs
>> similar logic, where IOMMU domains are created and devices attached to
>> compatible domains. Essentially mimmicing kernel
>> iommufd_device_auto_get_domain(). With mdevs given there's no IOMMU domain
>> it falls back to IOAS attach.
>>
>> The auto domain logic allows different IOMMU domains to be created when
>> DMA dirty tracking is not desired (and VF can provide it), and others where
>> it is. Here is not used in this way here given how VFIODevice migration
> 
> Here is not used in this way here ?
> 

I meant, 'Here it is not used in this way given (...)'

>> state is initialized after the device attachment. But such mixed mode of
>> IOMMU dirty tracking + device dirty tracking is an improvement that can
>> be added on. Keep the 'all of nothing' of type1 approach that we have
>> been using so far between container vs device dirty tracking.
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>  include/hw/vfio/vfio-common.h |  9 ++++
>>  include/sysemu/iommufd.h      |  5 +++
>>  backends/iommufd.c            | 30 +++++++++++++
>>  hw/vfio/iommufd.c             | 82 +++++++++++++++++++++++++++++++++++
>>  backends/trace-events         |  1 +
>>  5 files changed, 127 insertions(+)
>>
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index 7419466bca92..2dd468ce3c02 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -95,10 +95,17 @@ typedef struct VFIOHostDMAWindow {
>>  
>>  typedef struct IOMMUFDBackend IOMMUFDBackend;
>>  
>> +typedef struct VFIOIOASHwpt {
>> +    uint32_t hwpt_id;
>> +    QLIST_HEAD(, VFIODevice) device_list;
>> +    QLIST_ENTRY(VFIOIOASHwpt) next;
>> +} VFIOIOASHwpt;
>> +
>>  typedef struct VFIOIOMMUFDContainer {
>>      VFIOContainerBase bcontainer;
>>      IOMMUFDBackend *be;
>>      uint32_t ioas_id;
>> +    QLIST_HEAD(, VFIOIOASHwpt) hwpt_list;
>>  } VFIOIOMMUFDContainer;
>>  
>>  OBJECT_DECLARE_SIMPLE_TYPE(VFIOIOMMUFDContainer, VFIO_IOMMU_IOMMUFD);
>> @@ -135,6 +142,8 @@ typedef struct VFIODevice {
>>      HostIOMMUDevice *hiod;
>>      int devid;
>>      IOMMUFDBackend *iommufd;
>> +    VFIOIOASHwpt *hwpt;
>> +    QLIST_ENTRY(VFIODevice) hwpt_next;
>>  } VFIODevice;
>>  
>>  struct VFIODeviceOps {
>> diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
>> index 57d502a1c79a..e917e7591d05 100644
>> --- a/include/sysemu/iommufd.h
>> +++ b/include/sysemu/iommufd.h
>> @@ -50,6 +50,11 @@ int iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
>>  bool iommufd_backend_get_device_info(IOMMUFDBackend *be, uint32_t devid,
>>                                       uint32_t *type, void *data, uint32_t len,
>>                                       uint64_t *caps, Error **errp);
>> +bool iommufd_backend_alloc_hwpt(IOMMUFDBackend *be, uint32_t dev_id,
>> +                                uint32_t pt_id, uint32_t flags,
>> +                                uint32_t data_type, uint32_t data_len,
>> +                                void *data_ptr, uint32_t *out_hwpt,
>> +                                Error **errp);
>>  
>>  #define TYPE_HOST_IOMMU_DEVICE_IOMMUFD TYPE_HOST_IOMMU_DEVICE "-iommufd"
>>  #endif
>> diff --git a/backends/iommufd.c b/backends/iommufd.c
>> index 2b3d51af26d2..5d3dfa917415 100644
>> --- a/backends/iommufd.c
>> +++ b/backends/iommufd.c
>> @@ -208,6 +208,36 @@ int iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
>>      return ret;
>>  }
>>  
>> +bool iommufd_backend_alloc_hwpt(IOMMUFDBackend *be, uint32_t dev_id,
>> +                                uint32_t pt_id, uint32_t flags,
>> +                                uint32_t data_type, uint32_t data_len,
>> +                                void *data_ptr, uint32_t *out_hwpt,
>> +                                Error **errp)
>> +{
>> +    int ret, fd = be->fd;
>> +    struct iommu_hwpt_alloc alloc_hwpt = {
>> +        .size = sizeof(struct iommu_hwpt_alloc),
>> +        .flags = flags,
>> +        .dev_id = dev_id,
>> +        .pt_id = pt_id,
>> +        .data_type = data_type,
>> +        .data_len = data_len,
>> +        .data_uptr = (uint64_t)data_ptr,
>> +    };
>> +
>> +    ret = ioctl(fd, IOMMU_HWPT_ALLOC, &alloc_hwpt);
>> +    trace_iommufd_backend_alloc_hwpt(fd, dev_id, pt_id, flags, data_type,
>> +                                     data_len, (uint64_t)data_ptr,
>> +                                     alloc_hwpt.out_hwpt_id, ret);
>> +    if (ret) {
>> +        error_setg_errno(errp, errno, "Failed to allocate hwpt");
>> +        return false;
>> +    }
>> +
>> +    *out_hwpt = alloc_hwpt.out_hwpt_id;
>> +    return true;
>> +}
>> +
>>  bool iommufd_backend_get_device_info(IOMMUFDBackend *be, uint32_t devid,
>>                                       uint32_t *type, void *data, uint32_t len,
>>                                       uint64_t *caps, Error **errp)
>> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
>> index 077dea8f1b64..325c7598d5a1 100644
>> --- a/hw/vfio/iommufd.c
>> +++ b/hw/vfio/iommufd.c
>> @@ -212,10 +212,86 @@ static bool iommufd_cdev_detach_ioas_hwpt(VFIODevice *vbasedev, Error **errp)
>>      return true;
>>  }
>>  
>> +static bool iommufd_cdev_autodomains_get(VFIODevice *vbasedev,
>> +                                         VFIOIOMMUFDContainer *container,
>> +                                         Error **errp)
>> +{
>> +    IOMMUFDBackend *iommufd = vbasedev->iommufd;
>> +    uint32_t flags = 0;
>> +    VFIOIOASHwpt *hwpt;
>> +    uint32_t hwpt_id;
>> +    int ret;
>> +
>> +    /* Try to find a domain */
>> +    QLIST_FOREACH(hwpt, &container->hwpt_list, next) {
>> +        ret = iommufd_cdev_attach_ioas_hwpt(vbasedev, hwpt->hwpt_id, errp);
>> +        if (ret) {
>> +            /* -EINVAL means the domain is incompatible with the device. */
>> +            if (ret == -EINVAL) {
>> +                /*
>> +                 * It is an expected failure and it just means we will try
>> +                 * another domain, or create one if no existing compatible
>> +                 * domain is found. Hence why the error is discarded below.
>> +                 */
>> +                error_free(*errp);
>> +                *errp = NULL;
>> +                continue;
>> +            }
>> +
>> +            return false;
>> +        } else {
>> +            vbasedev->hwpt = hwpt;
>> +            QLIST_INSERT_HEAD(&hwpt->device_list, vbasedev, hwpt_next);
>> +            return true;
>> +        }
>> +    }
>> +
>> +    if (!iommufd_backend_alloc_hwpt(iommufd, vbasedev->devid,
>> +                                    container->ioas_id, flags,
>> +                                    IOMMU_HWPT_DATA_NONE, 0, NULL,
>> +                                    &hwpt_id, errp)) {
>> +        return false;
>> +    }
>> +
>> +    hwpt = g_malloc0(sizeof(*hwpt));
>> +    hwpt->hwpt_id = hwpt_id;
>> +    QLIST_INIT(&hwpt->device_list);
>> +
>> +    ret = iommufd_cdev_attach_ioas_hwpt(vbasedev, hwpt->hwpt_id, errp);
>> +    if (ret) {
>> +        iommufd_backend_free_id(container->be, hwpt->hwpt_id);
>> +        g_free(hwpt);
>> +        return false;
>> +    }
>> +
>> +    vbasedev->hwpt = hwpt;
>> +    QLIST_INSERT_HEAD(&hwpt->device_list, vbasedev, hwpt_next);
>> +    QLIST_INSERT_HEAD(&container->hwpt_list, hwpt, next);
>> +    return true;
>> +}
>> +
>> +static void iommufd_cdev_autodomains_put(VFIODevice *vbasedev,
>> +                                         VFIOIOMMUFDContainer *container)
>> +{
>> +    VFIOIOASHwpt *hwpt = vbasedev->hwpt;
>> +
>> +    QLIST_REMOVE(vbasedev, hwpt_next);
> don't you want to reset vbasedev->hwpt = NULL too?
> 
Yeap, Thanks for catching that

> 
>> +    if (QLIST_EMPTY(&hwpt->device_list)) {
>> +        QLIST_REMOVE(hwpt, next);
>> +        iommufd_backend_free_id(container->be, hwpt->hwpt_id);
>> +        g_free(hwpt);
>> +    }
>> +}
>> +
>>  static bool iommufd_cdev_attach_container(VFIODevice *vbasedev,
>>                                            VFIOIOMMUFDContainer *container,
>>                                            Error **errp)
>>  {
>> +    /* mdevs aren't physical devices and will fail with auto domains */
>> +    if (!vbasedev->mdev) {
>> +        return iommufd_cdev_autodomains_get(vbasedev, container, errp);
>> +    }
>> +
>>      return !iommufd_cdev_attach_ioas_hwpt(vbasedev, container->ioas_id, errp);
>>  }
>>  
>> @@ -224,6 +300,11 @@ static void iommufd_cdev_detach_container(VFIODevice *vbasedev,
>>  {
>>      Error *err = NULL;
>>  
>> +    if (vbasedev->hwpt) {
>> +        iommufd_cdev_autodomains_put(vbasedev, container);
>> +        return;
> Where do we detach the device from the hwpt?
> 
In iommufd_backend_free_id() for auto domains

> Thanks
> 
> Eric
>> +    }
>> +
>>      if (!iommufd_cdev_detach_ioas_hwpt(vbasedev, &err)) {
>>          error_report_err(err);
>>      }
>> @@ -354,6 +435,7 @@ static bool iommufd_cdev_attach(const char *name, VFIODevice *vbasedev,
>>      container = VFIO_IOMMU_IOMMUFD(object_new(TYPE_VFIO_IOMMU_IOMMUFD));
>>      container->be = vbasedev->iommufd;
>>      container->ioas_id = ioas_id;
>> +    QLIST_INIT(&container->hwpt_list);
>>  
>>      bcontainer = &container->bcontainer;
>>      vfio_address_space_insert(space, bcontainer);
>> diff --git a/backends/trace-events b/backends/trace-events
>> index 211e6f374adc..4d8ac02fe7d6 100644
>> --- a/backends/trace-events
>> +++ b/backends/trace-events
>> @@ -14,4 +14,5 @@ iommufd_backend_map_dma(int iommufd, uint32_t ioas, uint64_t iova, uint64_t size
>>  iommufd_backend_unmap_dma_non_exist(int iommufd, uint32_t ioas, uint64_t iova, uint64_t size, int ret) " Unmap nonexistent mapping: iommufd=%d ioas=%d iova=0x%"PRIx64" size=0x%"PRIx64" (%d)"
>>  iommufd_backend_unmap_dma(int iommufd, uint32_t ioas, uint64_t iova, uint64_t size, int ret) " iommufd=%d ioas=%d iova=0x%"PRIx64" size=0x%"PRIx64" (%d)"
>>  iommufd_backend_alloc_ioas(int iommufd, uint32_t ioas) " iommufd=%d ioas=%d"
>> +iommufd_backend_alloc_hwpt(int iommufd, uint32_t dev_id, uint32_t pt_id, uint32_t flags, uint32_t hwpt_type, uint32_t len, uint64_t data_ptr, uint32_t out_hwpt_id, int ret) " iommufd=%d dev_id=%u pt_id=%u flags=0x%x hwpt_type=%u len=%u data_ptr=0x%"PRIx64" out_hwpt=%u (%d)"
>>  iommufd_backend_free_id(int iommufd, uint32_t id, int ret) " iommufd=%d id=%d (%d)"
>