Re: [PATCH] drm/amdgpu: force using sdma to update vm page table when mmio is blocked

["Wang, Yang(Kevin)" <KevinYang.Wang@xxxxxxx>]

[AMD Official Use Only]

Thanks @Koenig, Christian.

Best Regards,

Kevin

---

From: Koenig, Christian <Christian.Koenig@xxxxxxx>
Sent: Thursday, January 20, 2022 5:11 PM
To: Wang, Yang(Kevin) <KevinYang.Wang@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Liu, Monk <Monk.Liu@xxxxxxx>
Cc: Min, Frank <Frank.Min@xxxxxxx>; Chen, Horace <Horace.Chen@xxxxxxx>
Subject: Re: [PATCH] drm/amdgpu: force using sdma to update vm page table when mmio is blocked

 

Hi Kevin,

well at least the HDP flush function has to work correctly or otherwise the driver won't work correctly.

If the registers are not accessible any more we need to find a proper workaround for this.

One possibility would be to use the KIQ, another is a dummy write/read to make sure the HDP is flushed (check the hardware docs).

The third option would be to question if blocking the HDP registers is really a good idea.

The solution is up to you, but a workaround like proposed below doesn't really help in any way.

Regards,
Christian.

Am 20.01.22 um 10:07 schrieb Wang, Yang(Kevin):

[AMD Official Use Only]

Hi Chris,

yes, I agree with your point.

and another way is that we can use KIQ to write HDP register to resolve HDP can't R/W issue.

but it will cause some performance drop if use KIQ to programing register.

what is your ideas?

Best Regards,

Kevin

---

From: Koenig, Christian <Christian.Koenig@xxxxxxx>
Sent: Thursday, January 20, 2022 4:58 PM
To: Wang, Yang(Kevin) <KevinYang.Wang@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Liu, Monk <Monk.Liu@xxxxxxx>
Cc: Min, Frank <Frank.Min@xxxxxxx>; Chen, Horace <Horace.Chen@xxxxxxx>
Subject: Re: [PATCH] drm/amdgpu: force using sdma to update vm page table when mmio is blocked

 

Well NAK.

Even when we can't R/W HDP registers we need a way to invalidate the HDP or quite a bunch of functions won't work correctly.

Blocking CPU base page table updates only works around the symptoms, but doesn't really solve anything.

Regards,
Christian.

Am 20.01.22 um 09:46 schrieb Wang, Yang(Kevin):

[AMD Official Use Only]

ping...

add @Liu, Monk @Koenig, Christian @Deucher, Alexander

Best Regards,

Kevin

---

From: Wang, Yang(Kevin) <KevinYang.Wang@xxxxxxx>
Sent: Wednesday, January 19, 2022 11:16 AM
To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>
Cc: Min, Frank <Frank.Min@xxxxxxx>; Chen, Horace <Horace.Chen@xxxxxxx>; Wang, Yang(Kevin) <KevinYang.Wang@xxxxxxx>
Subject: [PATCH] drm/amdgpu: force using sdma to update vm page table when mmio is blocked

 

when mmio protection feature is enabled in hypervisor,
it will cause guest OS can't R/W HDP regiters,
and using cpu to update page table is not working well.

force using sdma to update page table when mmio is blocked.

Signed-off-by: Yang Wang <KevinYang.Wang@xxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index b23cb463b106..0f86f0b2e183 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2959,6 +2959,9 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm)
         vm->use_cpu_for_update = !!(adev->vm_manager.vm_update_mode &
                                     AMDGPU_VM_USE_CPU_FOR_GFX);
 
+       if (vm->use_cpu_for_update && amdgpu_sriov_vf(adev) && amdgpu_virt_mmio_blocked(adev))
+               vm->use_cpu_for_update = false;
+
         DRM_DEBUG_DRIVER("VM update mode is %s\n",
                          vm->use_cpu_for_update ? "CPU" : "SDMA");
         WARN_ONCE((vm->use_cpu_for_update &&
@@ -3094,6 +3097,10 @@ int amdgpu_vm_make_compute(struct amdgpu_device *adev, struct amdgpu_vm *vm)
         /* Update VM state */
         vm->use_cpu_for_update = !!(adev->vm_manager.vm_update_mode &
                                     AMDGPU_VM_USE_CPU_FOR_COMPUTE);
+
+       if (vm->use_cpu_for_update && amdgpu_sriov_vf(adev) && amdgpu_virt_mmio_blocked(adev))
+               vm->use_cpu_for_update = false;
+
         DRM_DEBUG_DRIVER("VM update mode is %s\n",
                          vm->use_cpu_for_update ? "CPU" : "SDMA");
         WARN_ONCE((vm->use_cpu_for_update &&
--
2.25.1