[PATCH v6 0/5] Refactor default device atomic settings

[Lionel Landwerlin]

Since my understanding is that with this series we don't need to change 
anything in Mesa and atomics just work like on prior platforms, this v6 is :

Acked-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

Thanks a lot,

-Lionel

On 06/05/2024 10:13, Lionel Landwerlin wrote:
> On 03/05/2024 12:54, Nirmoy Das wrote:
>> Hi Lionel,
>>
>> On 5/3/2024 11:47 AM, Lionel Landwerlin wrote:
>>> Hi Nirmoy,
>>>
>>> I've updated our Mesa MR for this : 
>>> https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28823
>>>
>>> But then I started to wonder if we needed to do anything at all with 
>>> this v6.
>>
>> No, there is nothing to do for traditional APIs.
>>
>>
>>> The only scenario I'm not sure about is this : a BO is created with 
>>> 2 placements LMEM+SMEM. When Xe migrates the BO from LMEM to SMEM 
>>> due to LMEM pressure, does it set AE bit in the PTE?
>>> And then if promoted back to LMEM, is the PTE config DM=1 and AE=0 
>>> again?
>>
>>
>> For traditional API( not using fault/LR VM) then both backend will 
>> have AE=1, so on LMEM pressure if the buffer is backed by SMEM, it 
>> will have AE=1 as well.
>>
>>
>> Regards,
>>
>> Nirmoy
>
>
> Thanks a lot Nirmoy.
>
>
> Then I think with this series we should have everything working in 
> Mesa without having to change a single line of UMD.
>
>
> -Lionel
>
>
>>
>>>
>>> Thanks,
>>>
>>> -Lionel
>>>
>>> On 30/04/2024 19:25, Nirmoy Das wrote:
>>>> The default behavior of device atomics depends on the
>>>> VM type and buffer allocation types. Device atomics are
>>>> expected to function with all types of allocations for
>>>> traditional applications/APIs. Additionally, in compute/SVM
>>>> API scenarios with fault mode or LR mode VMs, device atomics
>>>> must work with single-region allocations. In all other cases
>>>> device atomics should be disabled by default. PVC needs special
>>>> care as it doesn't support device atomics on SMEM.
>>>>
>>>> v6: Only check LR mode to determine compute API as fault
>>>>      mode requires LR mode(Jose)
>>>>      Set AE=1 on SMEM+LMEM allocation when a buffer is migrated
>>>>      to LMEM from SMEM(Brian)
>>>>
>>>> v5: Fix broken atomics on PVC from v4 changes.
>>>>
>>>> v4: Previous assumption that device atomics should be disabled
>>>>      by default on SMEM only BO was wrong as traditional applications
>>>>      will not use such allocations for CPU atomics. So remove the
>>>>      VM bind flag and the query uAPI and instead refactor default 
>>>> device
>>>>      atomics settings as per VM type and buffer allocations.
>>>>
>>>>
>>>> v3: Capture ret value of xe_vm_bind_ioctl_validate_bo(Matt B).
>>>>      Remove redundant coh_mode param from 
>>>> xe_vm_bind_ioctl_validate_bo().
>>>>      Remove has_device_atomics_on_smem from xe_graphics_desc(Jose).
>>>>      Replace DRM_XE_QUERY_CONFIG_SUPP_DEV_ATOMIC_ON_SMEM with
>>>>      config flag 
>>>> DRM_XE_QUERY_CONFIG_FLAG_HAS_DEV_ATOMIC_ON_SMEM(Jose).
>>>>      Mention that PTE_AE will not be applied to userptr(Matt R)
>>>>
>>>> v2: Add BO helper func in xe_vm_bind_ioctl()(Matt B).
>>>>      Use XE_IOCTL_DBG for checks(Matt B).
>>>>      Move platform checks with help of adding flags in
>>>>      intel_device_info(Matt B).
>>>>      Add document for DRM_XE_VM_BIND_FLAG_DEVICE_ATOMICS(Matt B).
>>>>      Create query uAPI for this newly added VM bind flag(Jose, 
>>>> Lionel).
>>>>
>>>> Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan at intel.com>
>>>> Cc: Brian Welty <brian.welty at intel.com>
>>>> Cc: Fei Yang <fei.yang at intel.com>
>>>> Cc: Jose Souza <jose.souza at intel.com>
>>>> Cc: Lionel G Landwerlin <lionel.g.landwerlin at intel.com>
>>>> Cc: Matt Roper <matthew.d.roper at intel.com>
>>>> Cc: Matthew Brost <matthew.brost at intel.com>
>>>> Cc: Michal Mrozek <michal.mrozek at intel.com>
>>>> Cc: Oak Zeng <oak.zeng at intel.com>
>>>> Cc: Thomas Hellstr_m <thomas.hellstrom at linux.intel.com>
>>>>
>>>> Nirmoy Das (5):
>>>>    drm/xe: Introduce has_atomic_enable_pte_bit device info
>>>>    drm/xe: Move vm bind bo validation to a helper function
>>>>    drm/xe: Introduce has_device_atomics_on_smem device info
>>>>    drm/xe: Add function to check if BO has single placement
>>>>    drm/xe: Refactor default device atomic settings
>>>>
>>>>   drivers/gpu/drm/xe/xe_bo.c           | 14 +++++
>>>>   drivers/gpu/drm/xe/xe_bo.h           |  1 +
>>>>   drivers/gpu/drm/xe/xe_device_types.h |  4 ++
>>>>   drivers/gpu/drm/xe/xe_pci.c          |  5 ++
>>>>   drivers/gpu/drm/xe/xe_pci_types.h    |  1 +
>>>>   drivers/gpu/drm/xe/xe_pt.c           | 37 +++++++++++--
>>>>   drivers/gpu/drm/xe/xe_vm.c           | 79 
>>>> ++++++++++++++++------------
>>>>   7 files changed, 103 insertions(+), 38 deletions(-)
>>>>
>>>
>