[PATCH] drm/amdgpu/gmc11: disable AGP on GC 11.5

[Wang, Yang(Kevin)]

[AMD Official Use Only - General]

Hi Alex,

Does driver also need to disable AGP aperture in hardware side ? (Set register GCMC_VM_AGP_BOT/TOP to make AGP address range invalid).
The current changes only make the GPU not use AGP range addresses, but the hardware unit of AGP's aperture is still working.
There seems to be some hidden danger here, if the generates GPU an illegal address, then GPU can access it.

Ref commit: 81c274c473a2 drm/amdgpu: disable agp for sriov

Best Regards,
Kevin

-----Original Message-----
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Alex Deucher
Sent: Tuesday, September 19, 2023 10:38 PM
To: amd-gfx at lists.freedesktop.org
Cc: Deucher, Alexander <Alexander.Deucher at amd.com>
Subject: [PATCH] drm/amdgpu/gmc11: disable AGP on GC 11.5

AGP aperture is deprecated and no longer functional.

v2: fix typo (Alex)
v3: just skip the agp setup call

Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/gmc_v11_0.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v11_0.c b/drivers/gpu/drm/amd/amdgpu/gmc_v11_0.c
index 69f65e9c4f93..01cff4a3d4b1 100644
--- a/drivers/gpu/drm/amd/amdgpu/gmc_v11_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gmc_v11_0.c
@@ -689,7 +689,8 @@ static void gmc_v11_0_vram_gtt_location(struct amdgpu_device *adev,

        amdgpu_gmc_vram_location(adev, &adev->gmc, base);
        amdgpu_gmc_gart_location(adev, mc);
-       amdgpu_gmc_agp_location(adev, mc);
+       if (amdgpu_ip_version(adev, GC_HWIP, 0) < IP_VERSION(11, 5, 0))
+               amdgpu_gmc_agp_location(adev, mc);

        /* base offset of vram pages */
        if (amdgpu_sriov_vf(adev))
--
2.41.0