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Tue, 21 Apr 2026 06:42:33 -0700 (PDT) MIME-Version: 1.0 References: <20260420215717.223372-1-arjan@linux.intel.com> <34718f21-712a-4161-98e0-079dd9390ae6@amd.com> In-Reply-To: <34718f21-712a-4161-98e0-079dd9390ae6@amd.com> From: Alex Deucher Date: Tue, 21 Apr 2026 09:42:22 -0400 X-Gm-Features: AQROBzDeqv9bDX2RaJLbOqX6UXVA0203SVdcLBSCszkeeI82FwKP2sCJ2EAHOV4 Message-ID: Subject: Re: [PATCH] drm/amdgpu: fix zero-size GDS range init on RDNA4 To: =?UTF-8?Q?Christian_K=C3=B6nig?= Cc: arjan@linux.intel.com, amd-gfx@lists.freedesktop.org, Alex Deucher , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Apr 21, 2026 at 2:59=E2=80=AFAM Christian K=C3=B6nig wrote: > > On 4/20/26 23:57, arjan@linux.intel.com wrote: > > > > RDNA4 (GFX 12) hardware removes the GDS, GWS, and OA on-chip memory > > resources. The gfx_v12_0 initialisation code correctly leaves > > adev->gds.gds_size, adev->gds.gws_size, and adev->gds.oa_size at > > zero to reflect this. > > > > amdgpu_ttm_init() unconditionally calls amdgpu_ttm_init_on_chip() for > > each of these resources regardless of size. When the size is zero, > > amdgpu_ttm_init_on_chip() forwards the call to ttm_range_man_init(), > > which calls drm_mm_init(mm, 0, 0). drm_mm_init() immediately fires > > DRM_MM_BUG_ON(start + size <=3D start) -- trivially true when size is > > zero -- crashing the kernel during modprobe of amdgpu on an RX 9070 XT. > > Mhm in general not a bad idea, but we are having tons of GFX 12 systems i= n our test machines and nothing is crashing there. > > We are clearly missing something here. Is that on an upstream kernel or s= omething backported? Looks like that check only asserts if CONFIG_DRM_DEBUG_MM is set in the user's kernel config. I guess no one uses that option. These chips have been in the market for over a year and no one has reported that until now. Applied with a note about this in the commit message. Thanks! Alex > > Regards, > Christian. > > > > > Guard against this by returning 0 early from > > amdgpu_ttm_init_on_chip() when size_in_page is zero. This skips TTM > > resource manager registration for hardware resources that are absent, > > without affecting any other GPU type. > > > > Link: https://lore.kernel.org/all/bug-221376-2300@https.bugzilla.kernel= .org%2F/ > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D221376 > > Oops-Analysis: http://oops.fenrus.org/reports/bugzilla.korg/221376/repo= rt.html > > Assisted-by: GitHub Copilot:Claude Sonnet 4.6 linux-kernel-oops-x86. > > Signed-off-by: Arjan van de Ven > > Cc: Alex Deucher > > Cc: "Christian K=C3=B6nig" > > Cc: amd-gfx@lists.freedesktop.org > > Cc: dri-devel@lists.freedesktop.org > > Cc: linux-kernel@vger.kernel.org > > > > --- > > drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/= amd/amdgpu/amdgpu_ttm.c > > index afaaab6496def..8075ac735321e 100644 > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c > > @@ -75,6 +75,9 @@ static int amdgpu_ttm_init_on_chip(struct amdgpu_devi= ce *adev, > > unsigned int type, > > uint64_t size_in_page) > > { > > + if (!size_in_page) > > + return 0; > > + > > return ttm_range_man_init(&adev->mman.bdev, type, > > false, size_in_page); > > } >