Re: [PATCH v3 2/2] drm/amdgpu: Add TLB flush after MES user queue unmap

[Khatri, Sunil]

On 17-08-2026 07:49 pm, Alex Deucher wrote:
On Sun, Aug 16, 2026 at 1:25 PM Hosur, Priya <priya.ho...@amd.com> wrote:
AMD General


Hi Felix, Lijo,



Thanks for the clarification. I understand now - TLB flush is only needed after 
batch queue unmapping (eviction/suspension), not after each individual queue 
unmap.



Alex - based on Felix's feedback, the userq unmap path doesn't need the same 
fix since it's per-queue unmap rather than batch unmap.

I think it's still needed when we evict all KGD userqs for a process
(technically per GPU VM instance).  E.g., the eviction fence case.

@priya, i am looking into this in the KGD userqueues. It's ok if you 
drop that as it need some more insight to understand how well it fits 
the KGD queues..

Regards
Sunil Khatri


Alex


I'll drop patch 2/2 (userq fix) and send v4 with only the KFD fix.



Thanks and Regards,
Priya Hosur



From: Lazar, Lijo <lijo.la...@amd.com>
Sent: Friday, August 14, 2026 10:56 PM
To: Kuehling, Felix <felix.kuehl...@amd.com>; Hosur, Priya <priya.ho...@amd.com>; 
amd-gfx@lists.freedesktop.org; Deucher, Alexander <alexander.deuc...@amd.com>; Khatri, Sunil 
<sunil.kha...@amd.com>; Liu, Shaoyun <shaoyun....@amd.com>; Limonciello, Mario 
<mario.limoncie...@amd.com>; Koenig, Christian <christian.koe...@amd.com>
Cc: Vishwakarma, Pratik <pratik.vishwaka...@amd.com>; Gopalakrishnan, Veerabadhran 
(Veera) <veerabadhran.gopalakrish...@amd.com>
Subject: Re: [PATCH v3 2/2] drm/amdgpu: Add TLB flush after MES user queue unmap



AMD General



Thanks for the details. Didn't realise that it is one by one removal. I thought 
it was something like unmap-all for a PAS id.



Thanks,

Lijo

________________________________

From: Kuehling, Felix <felix.kuehl...@amd.com>
Sent: Friday, 14 August 2026 22:17:50
To: Lazar, Lijo <lijo.la...@amd.com>; Hosur, Priya <priya.ho...@amd.com>; amd-gfx@lists.freedesktop.org 
<amd-gfx@lists.freedesktop.org>; Deucher, Alexander <alexander.deuc...@amd.com>; Khatri, Sunil 
<sunil.kha...@amd.com>; Liu, Shaoyun <shaoyun....@amd.com>; Limonciello, Mario <mario.limoncie...@amd.com>; 
Koenig, Christian <christian.koe...@amd.com>
Cc: Vishwakarma, Pratik <pratik.vishwaka...@amd.com>; Gopalakrishnan, Veerabadhran 
(Veera) <veerabadhran.gopalakrish...@amd.com>
Subject: Re: [PATCH v3 2/2] drm/amdgpu: Add TLB flush after MES user queue unmap



AMD General



We don't need to flush TLBs after every queue unmap. We only need to do it if 
there is an expectation that memory access is quiesced after unmapping. In the 
case of KFD, we are doing it when we're unmapping all queues, e.g. in MMU 
notifiers, evictions or when the debugger needs to stop the queues and look at 
memory contents. We only need one TLB flush after unmapping many queues.



Therefore, MES should flush TLBs after every queue unmap. OTOH, MES must flush 
TLBs by itself when it switches VMIDs. This is not under driver control.



I don't know what the requirements are for quiescing memory access after 
unmapping amdgpu user mode queues.



Regards,

   Felix

________________________________

From: Lazar, Lijo <lijo.la...@amd.com>
Sent: Friday, August 14, 2026 12:29
To: Hosur, Priya <priya.ho...@amd.com>; amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; Deucher, 
Alexander <alexander.deuc...@amd.com>; Khatri, Sunil <sunil.kha...@amd.com>; Kuehling, Felix 
<felix.kuehl...@amd.com>; Liu, Shaoyun <shaoyun....@amd.com>; Limonciello, Mario <mario.limoncie...@amd.com>; 
Koenig, Christian <christian.koe...@amd.com>
Cc: Vishwakarma, Pratik <pratik.vishwaka...@amd.com>; Gopalakrishnan, Veerabadhran (Veera) 
<veerabadhran.gopalakrish...@amd.com>; Hosur, Priya <priya.ho...@amd.com>
Subject: Re: [PATCH v3 2/2] drm/amdgpu: Add TLB flush after MES user queue unmap



AMD General



Hi,



Shouldn't this be a FW fix?



Thanks,

Lijo

________________________________

From: Priya Hosur <priya.ho...@amd.com>
Sent: Friday, 14 August 2026 21:48:40
To: amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; Deucher, Alexander <alexander.deuc...@amd.com>; 
Khatri, Sunil <sunil.kha...@amd.com>; Kuehling, Felix <felix.kuehl...@amd.com>; Liu, Shaoyun 
<shaoyun....@amd.com>; Lazar, Lijo <lijo.la...@amd.com>; Limonciello, Mario <mario.limoncie...@amd.com>; 
Koenig, Christian <christian.koe...@amd.com>
Cc: Vishwakarma, Pratik <pratik.vishwaka...@amd.com>; Gopalakrishnan, Veerabadhran (Veera) 
<veerabadhran.gopalakrish...@amd.com>; Hosur, Priya <priya.ho...@amd.com>
Subject: [PATCH v3 2/2] drm/amdgpu: Add TLB flush after MES user queue unmap



Similar to the KFD fix, MES does not perform heavy-weight TLB
invalidation after unmapping user queues. Add
amdgpu_gmc_flush_gpu_tlb_pasid() after MES unmap succeeds in
amdgpu_userq_unmap_helper() to ensure in-flight memory accesses
complete before memory is freed or migrated.

Change-Id: I94fe2c84547723b6b73816ce8d727a54bd773a6a
Signed-off-by: Priya Hosur <priya.ho...@amd.com>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index 6d3ed55e9ab4..9fcf15d69b7b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -375,6 +375,12 @@ static int amdgpu_userq_unmap_helper(struct 
amdgpu_usermode_queue *queue)
                  } else {
                          trace_amdgpu_userq_state_changed(queue, 
AMDGPU_USERQ_STATE_UNMAPPED);
                          queue->state = AMDGPU_USERQ_STATE_UNMAPPED;
+                       /*
+                        * Heavy-weight TLB flush after MES unmaps queue to 
ensure
+                        * in-flight memory accesses complete before memory is 
freed/migrated.
+                        * MES does not do this automatically unlike HWS.
+                        */
+                       amdgpu_gmc_flush_gpu_tlb_pasid(adev, queue->vm->pasid, 
2, true, 0);
                  }
          }

--
2.43.0