[PATCH] drm/amdgpu: Add use_xgmi_p2p module parameter

[Felix Kuehling]

Am 2022-02-18 um 11:53 schrieb Alex Sierra:
> This parameter controls xGMI p2p communication, which is enabled by
> default. However, it can be disabled by setting it to 0. In case xGMI
> p2p is disabled in a dGPU, PCIe p2p interface will be used instead.
> This parameter is ignored in GPUs that do not support xGMI
> p2p configuration.
>
> Signed-off-by: Alex Sierra <alex.sierra at amd.com>
> Acked-by: Luben Tuikov <luben.tuikov at amd.com>
> Acked-by: Harish Kasiviswanathan <Harish.Kasiviswanathan at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu.h     | 1 +
>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 8 ++++++++
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c  | 4 ++--
>   3 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index f97848a0ed14..7e95d8bd2338 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -217,6 +217,7 @@ extern int amdgpu_mes;
>   extern int amdgpu_noretry;
>   extern int amdgpu_force_asic_type;
>   extern int amdgpu_smartshift_bias;
> +extern int amdgpu_use_xgmi_p2p;
>   #ifdef CONFIG_HSA_AMD
>   extern int sched_policy;
>   extern bool debug_evictions;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 2f8eafb6cf22..6156265f3178 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -181,6 +181,7 @@ int amdgpu_tmz = -1; /* auto */
>   int amdgpu_reset_method = -1; /* auto */
>   int amdgpu_num_kcq = -1;
>   int amdgpu_smartshift_bias;
> +int amdgpu_use_xgmi_p2p = -1;
>   
>   static void amdgpu_drv_delayed_reset_work_handler(struct work_struct *work);
>   
> @@ -677,6 +678,13 @@ MODULE_PARM_DESC(force_asic_type,
>   	"A non negative value used to specify the asic type for all supported GPUs");
>   module_param_named(force_asic_type, amdgpu_force_asic_type, int, 0444);
>   
> +/**
> + * DOC: use_xgmi_p2p (int)
> + * Enables/disables XGMI P2P interface (0 = disable, 1 = enable). The Default is -1 (enabled).
> + */
> +MODULE_PARM_DESC(use_xgmi_p2p,
> +	"Disable XGMI P2P interface (0 = disable; 1 = enable; -1 default, enabled)");
> +module_param_named(use_xgmi_p2p, amdgpu_use_xgmi_p2p, int, 0444);
>   
>   
>   #ifdef CONFIG_HSA_AMD
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 207cd01435b5..bbe1bac61f15 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -2330,8 +2330,8 @@ struct amdgpu_bo_va *amdgpu_vm_bo_add(struct amdgpu_device *adev,
>   #else
>   	dma_resv_assert_held(amdkcl_ttm_resvp(&vm->root.bo->tbo));
>   #endif
> -
> -	if (amdgpu_dmabuf_is_xgmi_accessible(adev, bo)) {
> +	if (amdgpu_use_xgmi_p2p &&
> +	    amdgpu_dmabuf_is_xgmi_accessible(adev, bo)) {
This does nothing to tell user mode that XGMI is not available. We need 
to update the topology information as well. For that, this check needs 
to be applied at a lower level. I think amdgpu_xgmi_same_hive would be 
the right place. If amdgpu_use_xgmi_p2p is set, amdgpu_xgmi_same_hive 
should return false.

Regards,
   Felix


>   		bo_va->is_xgmi = true;
>   		/* Power up XGMI if it can be potentially used */
>   		amdgpu_xgmi_set_pstate(adev, AMDGPU_XGMI_PSTATE_MAX_VEGA20);