Re: [PATCH v6 4/9] vfio/{iommufd,container}: Invoke HostIOMMUDevice::realize() during attach_device()

[Eric Auger]

On 7/23/24 10:20, Duan, Zhenzhong wrote:
>
>> -----Original Message-----
>> From: Joao Martins <joao.m.martins@oracle.com>
>> Subject: Re: [PATCH v6 4/9] vfio/{iommufd,container}: Invoke
>> HostIOMMUDevice::realize() during attach_device()
>>
>> On 23/07/2024 08:55, Eric Auger wrote:
>>>
>>> On 7/23/24 09:44, Cédric Le Goater wrote:
>>>> On 7/23/24 09:38, Eric Auger wrote:
>>>>> Hi Joao,
>>>>>
>>>>> On 7/22/24 23:13, Joao Martins wrote:
>>>>>> Move the HostIOMMUDevice::realize() to be invoked during the attach
>>>>>> of the device
>>>>>> before we allocate IOMMUFD hardware pagetable objects (HWPT). This
>>>>>> allows the use
>>>>>> of the hw_caps obtained by IOMMU_GET_HW_INFO that essentially
>> tell
>>>>>> if the IOMMU
>>>>>> behind the device supports dirty tracking.
>>>>>>
>>>>>> Note: The HostIOMMUDevice data from legacy backend is static and
>>>>>> doesn't
>>>>>> need any information from the (type1-iommu) backend to be
>> initialized.
>>>>>> In contrast however, the IOMMUFD HostIOMMUDevice data requires
>> the
>>>>>> iommufd FD to be connected and having a devid to be able to
>>>>>> successfully
>>>>> Nit: maybe this comment shall be also added in iommufd.c before the
>> call
>>>>> to vfio_device_hiod_realize() to avoid someone else to move that call
>>>>> earlier at some point
>>>>>> GET_HW_INFO. This means vfio_device_hiod_realize() is called in
>>>>>> different places within the backend .attach_device() implementation.
>>>>>>
>>>>>> Suggested-by: Cédric Le Goater <clg@redhat.cm>
>>>>>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>>>>>> Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>>>>> ---
>>>>>>   include/hw/vfio/vfio-common.h |  1 +
>>>>>>   hw/vfio/common.c              | 16 ++++++----------
>>>>>>   hw/vfio/container.c           |  4 ++++
>>>>>>   hw/vfio/helpers.c             | 11 +++++++++++
>>>>>>   hw/vfio/iommufd.c             |  4 ++++
>>>>>>   5 files changed, 26 insertions(+), 10 deletions(-)
>>>>>>
>>>>>> diff --git a/include/hw/vfio/vfio-common.h
>>>>>> b/include/hw/vfio/vfio-common.h
>>>>>> index 1a96678f8c38..4e44b26d3c45 100644
>>>>>> --- a/include/hw/vfio/vfio-common.h
>>>>>> +++ b/include/hw/vfio/vfio-common.h
>>>>>> @@ -242,6 +242,7 @@ void vfio_region_finalize(VFIORegion *region);
>>>>>>   void vfio_reset_handler(void *opaque);
>>>>>>   struct vfio_device_info *vfio_get_device_info(int fd);
>>>>>>   bool vfio_device_is_mdev(VFIODevice *vbasedev);
>>>>>> +bool vfio_device_hiod_realize(VFIODevice *vbasedev, Error **errp);
>>>>>>   bool vfio_attach_device(char *name, VFIODevice *vbasedev,
>>>>>>                           AddressSpace *as, Error **errp);
>>>>>>   void vfio_detach_device(VFIODevice *vbasedev);
>>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>>>>>> index 784e266e6aab..da12cbd56408 100644
>>>>>> --- a/hw/vfio/common.c
>>>>>> +++ b/hw/vfio/common.c
>>>>>> @@ -1537,7 +1537,7 @@ bool vfio_attach_device(char *name,
>> VFIODevice
>>>>>> *vbasedev,
>>>>>>   {
>>>>>>       const VFIOIOMMUClass *ops =
>>>>>>
>>>>>>
>> VFIO_IOMMU_CLASS(object_class_by_name(TYPE_VFIO_IOMMU_LEGACY));
>>>>>> -    HostIOMMUDevice *hiod;
>>>>>> +    HostIOMMUDevice *hiod = NULL;
>>>>>>         if (vbasedev->iommufd) {
>>>>>>           ops =
>>>>>>
>> VFIO_IOMMU_CLASS(object_class_by_name(TYPE_VFIO_IOMMU_IOMMUF
>> D));
>>>>>> @@ -1545,21 +1545,17 @@ bool vfio_attach_device(char *name,
>>>>>> VFIODevice *vbasedev,
>>>>>>         assert(ops);
>>>>>>   -    if (!ops->attach_device(name, vbasedev, as, errp)) {
>>>>>> -        return false;
>>>>>> -    }
>>>>>>   -    if (vbasedev->mdev) {
>>>>>> -        return true;
>>>>>> +    if (!vbasedev->mdev) {
>>>>>> +        hiod = HOST_IOMMU_DEVICE(object_new(ops-
>>> hiod_typename));
>>>>>> +        vbasedev->hiod = hiod;
>>>>>>       }
>>>>>>   -    hiod = HOST_IOMMU_DEVICE(object_new(ops->hiod_typename));
>>>>>> -    if (!HOST_IOMMU_DEVICE_GET_CLASS(hiod)->realize(hiod,
>> vbasedev,
>>>>>> errp)) {
>>>>>> +    if (!ops->attach_device(name, vbasedev, as, errp)) {
>>>>>>           object_unref(hiod);
>>>>>> -        ops->detach_device(vbasedev);
>>>>>> +        vbasedev->hiod = NULL;
>>>>>>           return false;
>>>>>>       }
>>>>>> -    vbasedev->hiod = hiod;
>>>>>>         return true;
>>>>>>   }
>>>>>> diff --git a/hw/vfio/container.c b/hw/vfio/container.c
>>>>>> index 10cb4b4320ac..9ccdb639ac84 100644
>>>>>> --- a/hw/vfio/container.c
>>>>>> +++ b/hw/vfio/container.c
>>>>>> @@ -914,6 +914,10 @@ static bool vfio_legacy_attach_device(const
>>>>>> char *name, VFIODevice *vbasedev,
>>>>>>         trace_vfio_attach_device(vbasedev->name, groupid);
>>>>>>   +    if (!vfio_device_hiod_realize(vbasedev, errp)) {
>>>>>> +        return false;
>>>>> don't you want to go to err_alloc_ioas instead?
>>>> hmm, the err_alloc_ioas label is in a different function
>>>> iommufd_cdev_attach().
>>>>
>>>> may be you meant the comment for routine iommufd_cdev_attach() and
>>>> label err_connect_bind ?
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> C.
>>>>
>>>>
>>>>>> +    }
>>>>>> +
>>>>>>       group = vfio_get_group(groupid, as, errp);
>>>>>>       if (!group) {
>>>>>>           return false;
>>>>>> diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
>>>>>> index 7e23e9080c9d..ea15c79db0a3 100644
>>>>>> --- a/hw/vfio/helpers.c
>>>>>> +++ b/hw/vfio/helpers.c
>>>>>> @@ -689,3 +689,14 @@ bool vfio_device_is_mdev(VFIODevice
>> *vbasedev)
>>>>>>       subsys = realpath(tmp, NULL);
>>>>>>       return subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
>>>>>>   }
>>>>>> +
>>>>>> +bool vfio_device_hiod_realize(VFIODevice *vbasedev, Error **errp)
>>>>>> +{
>>>>>> +    HostIOMMUDevice *hiod = vbasedev->hiod;
>>>>>> +
>>>>>> +    if (!hiod) {
>>>>>> +        return true;
>>>>>> +    }
>>>>>> +
>>>>>> +    return HOST_IOMMU_DEVICE_GET_CLASS(hiod)->realize(hiod,
>>>>>> vbasedev, errp);
>>>>>> +}
>>>>>> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
>>>>>> index 5e2fc1ce089d..2324bf892c56 100644
>>>>>> --- a/hw/vfio/iommufd.c
>>>>>> +++ b/hw/vfio/iommufd.c
>>>>>> @@ -403,6 +403,10 @@ static bool iommufd_cdev_attach(const char
>>>>>> *name, VFIODevice *vbasedev,
>>>>>>         space = vfio_get_address_space(as);
>>>>>>   +    if (!vfio_device_hiod_realize(vbasedev, errp)) {
>>>>>> +        return false;
>>> Hum sorry my previous comment was targetting that place. I think
>>> unrolling is needed up to put_address_space
>>>
>>> so effectively this does not match err_alloc_ioas but I guess we would
>>> need another label
>>>
>> You're right. We haven't yet attached rthe device and that's what
>> err_alloc_ioas
>> would do. Adding another label not sure would make things cleaner given
>> the
>> ordering requirement. So maybe this instead?
>>
>> @@ -482,7 +483,8 @@ static bool iommufd_cdev_attach(const char *name,
>> VFIODevice
>> *vbasedev,
>>     space = vfio_get_address_space(as);
>>
>>     if (!vfio_device_hiod_realize(vbasedev, errp)) {
>> -        return false;
>> +        vfio_put_address_space(space);
>> +        goto err_connect_bind;
>>     }
>>
>>     /* try to attach to an existing container in this space */
> I was confused though Cedric and Eric both ACK this change. Don't we miss the 
> iommufd_cdev_unbind_and_disconnect() call?
Hum yes you're right. connect and bind was done. I thought this was done
later. so err_alloc_ioas label looks good

Eric
>