Re: [PATCH 1/2] drm/xe: Add feature to force ring-based TLB invalidations

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Jan 14, 2026 at 12:04:20AM +0000, Stuart Summers wrote:
> Current hardware does an implicit TLB invalidation on
> context switch. This is required for various use cases like
> preempt fences where a context switch will happen without
> any explicit TLB invalidation from the KMD.
> 
> Add a hook to make this explicit as part of the ring
> prior to batch execution to allow for more explicit testing
> and sequencing of user batch execution.
> 

I don't this patch is needed rather this an existing bug in xe_pt.c...

1974                 if ((!pt_op->rebind && xe_vm_has_scratch(vm) &&
1975                      xe_vm_in_lr_mode(vm)))
1976                         pt_update_ops->needs_invalidation = true;
1977                 else if (pt_op->rebind && !xe_vm_in_lr_mode(vm))
1978                         /* We bump also if batch_invalidate_tlb is true */
1979                         vm->tlb_flush_seqno++;

I believe we also need this at the end:

else if (pt_op->rebind)
	pt_update_ops->needs_invalidation = true;

My question is: does this patch internally change failure rates? If so,
I believe implicit TLB invalidation is hiding a bug in the current
IGT suite/KMD/hardware that just hasn’t been caught yet.

Matt

> Signed-off-by: Akshata Jahagirdar <akshata.jahagirdar@intel.com>
> Signed-off-by: Stuart Summers <stuart.summers@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_device_types.h | 2 ++
>  drivers/gpu/drm/xe/xe_pci.c          | 1 +
>  drivers/gpu/drm/xe/xe_pci_types.h    | 1 +
>  drivers/gpu/drm/xe/xe_sched_job.c    | 7 +++++--
>  drivers/gpu/drm/xe/xe_vm.c           | 3 +++
>  5 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
> index f689766adcb1..fa193e0b906d 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -355,6 +355,8 @@ struct xe_device {
>  		u8 has_pxp:1;
>  		/** @info.has_range_tlb_inval: Has range based TLB invalidations */
>  		u8 has_range_tlb_inval:1;
> +		/** @info.has_ring_tlb_inval: Performs TLB invalidations on context switch */
> +		u8 has_ring_tlb_inval:1;
>  		/** @info.has_soc_remapper_sysctrl: Has SoC remapper system controller */
>  		u8 has_soc_remapper_sysctrl:1;
>  		/** @info.has_soc_remapper_telem: Has SoC remapper telemetry support */
> diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> index 5c705124270e..a2ce9da2e3cb 100644
> --- a/drivers/gpu/drm/xe/xe_pci.c
> +++ b/drivers/gpu/drm/xe/xe_pci.c
> @@ -893,6 +893,7 @@ static int xe_info_init(struct xe_device *xe,
>  		xe->info.has_device_atomics_on_smem = 1;
>  
>  	xe->info.has_range_tlb_inval = graphics_desc->has_range_tlb_inval;
> +	xe->info.has_ring_tlb_inval = graphics_desc->has_ring_tlb_inval;
>  	xe->info.has_usm = graphics_desc->has_usm;
>  	xe->info.has_64bit_timestamp = graphics_desc->has_64bit_timestamp;
>  
> diff --git a/drivers/gpu/drm/xe/xe_pci_types.h b/drivers/gpu/drm/xe/xe_pci_types.h
> index 20acc5349ee6..783ebda6eae1 100644
> --- a/drivers/gpu/drm/xe/xe_pci_types.h
> +++ b/drivers/gpu/drm/xe/xe_pci_types.h
> @@ -72,6 +72,7 @@ struct xe_graphics_desc {
>  	u8 has_atomic_enable_pte_bit:1;
>  	u8 has_indirect_ring_state:1;
>  	u8 has_range_tlb_inval:1;
> +	u8 has_ring_tlb_inval:1;
>  	u8 has_usm:1;
>  	u8 has_64bit_timestamp:1;
>  };
> diff --git a/drivers/gpu/drm/xe/xe_sched_job.c b/drivers/gpu/drm/xe/xe_sched_job.c
> index 39aec7f6d86d..c3b3d9c56dbb 100644
> --- a/drivers/gpu/drm/xe/xe_sched_job.c
> +++ b/drivers/gpu/drm/xe/xe_sched_job.c
> @@ -246,6 +246,7 @@ bool xe_sched_job_completed(struct xe_sched_job *job)
>  void xe_sched_job_arm(struct xe_sched_job *job)
>  {
>  	struct xe_exec_queue *q = job->q;
> +	struct xe_device *xe = gt_to_xe(q->gt);
>  	struct dma_fence *fence, *prev;
>  	struct xe_vm *vm = q->vm;
>  	u64 seqno = 0;
> @@ -259,9 +260,11 @@ void xe_sched_job_arm(struct xe_sched_job *job)
>  			xe_vm_assert_held(q->vm);
>  	}
>  
> -	if (vm && !xe_sched_job_is_migration(q) && !xe_vm_in_lr_mode(vm) &&
> +	if (vm && !xe_sched_job_is_migration(q) &&
> +	    (xe->info.has_ring_tlb_inval || !xe_vm_in_lr_mode(vm)) &&
>  	    (vm->batch_invalidate_tlb || vm->tlb_flush_seqno != q->tlb_flush_seqno)) {
> -		xe_vm_assert_held(vm);
> +		if (!xe->info.has_ring_tlb_inval)
> +			xe_vm_assert_held(vm);
>  		q->tlb_flush_seqno = vm->tlb_flush_seqno;
>  		job->ring_ops_flush_tlb = true;
>  	}
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 694f592a0f01..8e0ba2eba21e 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -1619,6 +1619,9 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags, struct xe_file *xef)
>  			vm->batch_invalidate_tlb = false;
>  		}
>  
> +		if (xe->info.has_ring_tlb_inval)
> +			vm->batch_invalidate_tlb = true;
> +
>  		/* Fill pt_root after allocating scratch tables */
>  		for_each_tile(tile, xe, id) {
>  			if (!vm->pt_root[id])
> -- 
> 2.34.1
>