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

[Joao Martins]

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_IOMMUFD));
>>>> @@ -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 */