Re: [PATCH v6 6/9] vfio/iommufd: Implement VFIOIOMMUClass::set_dirty_tracking support

[Eric Auger <eric.auger@redhat.com>]

On 7/23/24 10:14, Joao Martins wrote:
> On 23/07/2024 09:03, Eric Auger wrote:
>> Hi Joao,
>>
>> On 7/22/24 23:13, Joao Martins wrote:
>>> ioctl(iommufd, IOMMU_HWPT_SET_DIRTY_TRACKING, arg) is the UAPI that
>>> enables or disables dirty page tracking. The ioctl is used if the hwpt
>>> has been created with dirty tracking supported domain (stored in
>>> hwpt::flags) and it is called on the whole list of iommu domains.
>>>
>>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>>> Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>> ---
>>>  include/sysemu/iommufd.h |  2 ++
>>>  backends/iommufd.c       | 23 +++++++++++++++++++++++
>>>  hw/vfio/iommufd.c        | 32 ++++++++++++++++++++++++++++++++
>>>  backends/trace-events    |  1 +
>>>  4 files changed, 58 insertions(+)
>>>
>>> diff --git a/include/sysemu/iommufd.h b/include/sysemu/iommufd.h
>>> index e917e7591d05..6fb412f61144 100644
>>> --- a/include/sysemu/iommufd.h
>>> +++ b/include/sysemu/iommufd.h
>>> @@ -55,6 +55,8 @@ bool iommufd_backend_alloc_hwpt(IOMMUFDBackend *be, uint32_t dev_id,
>>>                                  uint32_t data_type, uint32_t data_len,
>>>                                  void *data_ptr, uint32_t *out_hwpt,
>>>                                  Error **errp);
>>> +bool iommufd_backend_set_dirty_tracking(IOMMUFDBackend *be, uint32_t hwpt_id,
>>> +                                        bool start, 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 06b135111f30..b97883503884 100644
>>> --- a/backends/iommufd.c
>>> +++ b/backends/iommufd.c
>>> @@ -238,6 +238,29 @@ bool iommufd_backend_alloc_hwpt(IOMMUFDBackend *be, uint32_t dev_id,
>>>      return true;
>>>  }
>>>  
>>> +bool iommufd_backend_set_dirty_tracking(IOMMUFDBackend *be,
>>> +                                        uint32_t hwpt_id, bool start,
>>> +                                        Error **errp)
>>> +{
>>> +    int ret;
>>> +    struct iommu_hwpt_set_dirty_tracking set_dirty = {
>>> +            .size = sizeof(set_dirty),
>>> +            .hwpt_id = hwpt_id,
>>> +            .flags = start ? IOMMU_HWPT_DIRTY_TRACKING_ENABLE : 0,
>>> +    };
>>> +
>>> +    ret = ioctl(be->fd, IOMMU_HWPT_SET_DIRTY_TRACKING, &set_dirty);
>>> +    trace_iommufd_backend_set_dirty(be->fd, hwpt_id, start, ret ? errno : 0);
>>> +    if (ret) {
>>> +        error_setg_errno(errp, errno,
>>> +                         "IOMMU_HWPT_SET_DIRTY_TRACKING(hwpt_id %u) failed",
>>> +                         hwpt_id);
>>> +        return false;
>>> +    }
>>> +
>>> +    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 7afea0b041ed..b882a3f59a6e 100644
>>> --- a/hw/vfio/iommufd.c
>>> +++ b/hw/vfio/iommufd.c
>>> @@ -115,6 +115,37 @@ static bool iommufd_hwpt_dirty_tracking(VFIOIOASHwpt *hwpt)
>>>      return hwpt && hwpt->hwpt_flags & IOMMU_HWPT_ALLOC_DIRTY_TRACKING;
>>>  }
>>>  
>>> +static int iommufd_set_dirty_page_tracking(const VFIOContainerBase *bcontainer,
>>> +                                           bool start, Error **errp)
>>> +{
>>> +    const VFIOIOMMUFDContainer *container =
>>> +        container_of(bcontainer, VFIOIOMMUFDContainer, bcontainer);
>>> +    VFIOIOASHwpt *hwpt;
>>> +
>>> +    QLIST_FOREACH(hwpt, &container->hwpt_list, next) {
>>> +        if (!iommufd_hwpt_dirty_tracking(hwpt)) {
>>> +            continue;
>>> +        }
>> so here I see you handle the case where we have hwpts with and without
>> support for dirty tracking within the same container so I guess this
>> answers my previous question. So do you want to tag a container as
>> dirty_pages_supported = true as soon as one device is backed up with a
>> dirty tracking hwpt within that container? I think I miss the high level
>> view of when this case may happen and why the devices do not end up in
>> different containers/ioas. But maybe I completely mix up things &
>> objects. Eric
> I think the only gap I have in this series that I don't catch exactly right in
> all this logic, is when the IOMMU dirty tracking is not homogeneous, which
> remains to be seen in pratice (from h/w perspective). That's where we currently
> have a gap here. Other than that, either we do 'all VFs do dirty tracking' or
> 'all devices are backed by IOMMU'.
>
> A container may have different hwpt with different capabilities e.g. systems
> where IOMMU instances have different dirty tracking ability (again I don't know
> if these exist). Which, on hwpt without dirty tracking, on which the devices
> attached to it that lack VF dirty tracking should be added an LM blocker.
>
> These checks were added from the previous cycles, but I was actually thinking in
> making these g_assert() to make sure this is not exercised like that. But
> considering I plan on improve a mixed usage of VF dirty tracking with IOMMU I
> left them as simply checks.

OK fair enough. Keeping that in mind for future consolidations

Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
>
>>> +
>>> +        if (!iommufd_backend_set_dirty_tracking(container->be,
>>> +                                                hwpt->hwpt_id, start, errp)) {
>>> +            goto err;
>>> +        }
>>> +    }
>>> +
>>> +    return 0;
>>> +
>>> +err:
>>> +    QLIST_FOREACH(hwpt, &container->hwpt_list, next) {
>>> +        if (!iommufd_hwpt_dirty_tracking(hwpt)) {
>>> +            continue;
>>> +        }
>>> +        iommufd_backend_set_dirty_tracking(container->be,
>>> +                                           hwpt->hwpt_id, !start, NULL);
>>> +    }
>>> +    return -EINVAL;
>>> +}
>>> +
>>>  static int iommufd_cdev_getfd(const char *sysfs_path, Error **errp)
>>>  {
>>>      ERRP_GUARD();
>>> @@ -725,6 +756,7 @@ static void vfio_iommu_iommufd_class_init(ObjectClass *klass, void *data)
>>>      vioc->attach_device = iommufd_cdev_attach;
>>>      vioc->detach_device = iommufd_cdev_detach;
>>>      vioc->pci_hot_reset = iommufd_cdev_pci_hot_reset;
>>> +    vioc->set_dirty_page_tracking = iommufd_set_dirty_page_tracking;
>>>  };
>>>  
>>>  static bool hiod_iommufd_vfio_realize(HostIOMMUDevice *hiod, void *opaque,
>>> diff --git a/backends/trace-events b/backends/trace-events
>>> index 4d8ac02fe7d6..28aca3b859d4 100644
>>> --- a/backends/trace-events
>>> +++ b/backends/trace-events
>>> @@ -16,3 +16,4 @@ iommufd_backend_unmap_dma(int iommufd, uint32_t ioas, uint64_t iova, uint64_t si
>>>  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)"
>>> +iommufd_backend_set_dirty(int iommufd, uint32_t hwpt_id, bool start, int ret) " iommufd=%d hwpt=%u enable=%d (%d)"