Re: [PATCH 3/3] drm/xe/pf: Invalidate LMTT after completing changes

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

On 03.07.2025 00:41, Matthew Brost wrote:
> On Thu, Jul 03, 2025 at 12:30:41AM +0200, Michal Wajdeczko wrote:
>> Once we finish populating all leaf pages in the VF's LMTT we should
>> make sure that hardware will not access any stale data. Explicitly
>> force LMTT invalidation (as it was already planned in the past).
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>> Cc: Michał Winiarski <michal.winiarski@intel.com>
>> Cc: Piotr Piórkowski <piotr.piorkowski@intel.com>
>> ---
>>  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c | 12 +++++++++++-
>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
>> index a75ef4007a1e..a1b916e80fdd 100644
>> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
>> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
>> @@ -1327,7 +1327,17 @@ static int pf_distribute_config_lmem(struct xe_gt *gt, unsigned int vfid, u64 si
>>  
>>  static void pf_force_lmtt_invalidate(struct xe_device *xe)
>>  {
>> -	/* TODO */
>> +	struct xe_lmtt *lmtt;
>> +	struct xe_tile *tile;
>> +	unsigned int tid;
>> +
>> +	xe_assert(xe, xe_device_has_lmtt(xe));
>> +	xe_assert(xe, IS_SRIOV_PF(xe));
>> +
>> +	for_each_tile(tile, xe, tid) {
>> +		lmtt = &tile->sriov.pf.lmtt;
>> +		xe_lmtt_invalidate_hw(lmtt);
> 
> If this is a critical path, you may want to consider issuing all TLB
> invalidations across all GTs/tiles, then waiting on all fences to
> pipeline these - we do this the VM code which is certainly a critical
> path. If this is not-so-critical here, maybe this is ok.

no, it's not on any critical path right now and btw I already have some
hybrid solution: first I'm sending TLBINVAL to all GTs per tile and then
waiting for those fences, as this was more self contained from the LMTT
SW component POV (since it's per-tile)

> 
> Matt
> 
>> +	}
>>  }
>>  
>>  static void pf_reset_vf_lmtt(struct xe_device *xe, unsigned int vfid)
>> -- 
>> 2.47.1
>>