From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E9C732C5DF; Sun, 1 Jun 2025 23:43:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748821404; cv=none; b=Fq8faEPDbRGoHn7NMVxuNVoYADDsgKcDgnahchXg4iue5Prz4tI0XqO8+2yg73ihyI4afm7jizgoHBcHY5xSd0L2jl6zKUyOR009MfJa6zQDTYdvUxU3Iz8ETNDpfGi42yvzIspV8UfsCWKRiaWMC0eJuQ7rfD0ABprTR/6RCh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748821404; c=relaxed/simple; bh=fKSTeMep0yhUG+03V6f/afAYBcWpK730LxPz53maChw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=gd/ROeDt8kNIQQg1JktfLD6Ftt3iH1073MgyAm9iyCMQvvAXwCrDJ19KT9hZL6+N0wI3oUUyOcmxbx02hHzjMCYFSGt0Bg6JYfgi9BF6EiWmYgaqVpBS0d4Hif1ncc1VKngEmSli2T3DaTj13YUqEUSvJ8XlATTXPqk/Aq6FnTU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bxkr/TsD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bxkr/TsD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DFB09C4CEEE; Sun, 1 Jun 2025 23:43:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748821403; bh=fKSTeMep0yhUG+03V6f/afAYBcWpK730LxPz53maChw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bxkr/TsDxj9pk9rB7YsJWtPf2EIanoJEATk2o/YeLEImBrro3JsAXRW9pYO66lphW 0A7SdfzLx5K6lSn4OfRJ9qKgr5r8FFlSTekiUQz4DV9HpHj7qSbLmVy4ekOwa7Lfov AHw1CClfTFrlPfeh74TuM04XH9Hq8nqmWN43Wfr3cWh4wQC6OWXkD2yusXGTvA6SIG jP6MfczCEgerfxpFyMWUF+w+JNF3bkaLx2VQ1RK0GeX+ht9qHNvxZ94zAs81nO7xW6 5FhLFMbLLv56nQenz8t32Uk1FPOUKRhSOOpvB1og7FAnfNZoXEH0GDGE9jHXmXrjJ2 BksgP9sYNo8Mw== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Alex Deucher , Rodrigo Siqueira , Sasha Levin , christian.koenig@amd.com, airlied@gmail.com, simona@ffwll.ch, sunil.khatri@amd.com, vitaly.prosyak@amd.com, srinivasan.shanmugam@amd.com, Jiadong.Zhu@amd.com, kevinyang.wang@amd.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 25/43] drm/amdgpu/gfx9: fix CSIB handling Date: Sun, 1 Jun 2025 19:42:05 -0400 Message-Id: <20250601234224.3517599-25-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250601234224.3517599-1-sashal@kernel.org> References: <20250601234224.3517599-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.15.184 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Alex Deucher [ Upstream commit a4a4c0ae6742ec7d6bf1548d2c6828de440814a0 ] We shouldn't return after the last section. We need to update the rest of the CSIB. Reviewed-by: Rodrigo Siqueira Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- Now I'll analyze the specific code changes and provide my backport recommendation: **YES** This commit should be backported to stable kernel trees. Here's my detailed analysis: ## Code Analysis The commit fixes a logic bug in the `gfx_v9_0_get_csb_buffer()` function that builds GPU command buffers for AMD GFX9 hardware. Looking at the code change: **Before:** ```c if (sect->id == SECT_CONTEXT) { buffer[count++] = cpu_to_le32(PACKET3(PACKET3_SET_CONTEXT_REG, ext->reg_count)); buffer[count++] = cpu_to_le32(ext->reg_index - PACKET3_SET_CONTEXT_REG_START); for (i = 0; i < ext->reg_count; i++) buffer[count++] = cpu_to_le32(ext->extent[i]); } else { return; // ← BUGGY early return } ``` **After:** ```c if (sect->id == SECT_CONTEXT) { buffer[count++] = cpu_to_le32(PACKET3(PACKET3_SET_CONTEXT_REG, ext->reg_count)); buffer[count++] = cpu_to_le32(ext->reg_index - PACKET3_SET_CONTEXT_REG_START); for (i = 0; i < ext->reg_count; i++) buffer[count++] = cpu_to_le32(ext->extent[i]); } // ← Early return removed, execution continues ``` ## Why This Should Be Backported ### 1. **Fixes a Clear Logic Bug** The early return prevents the function from completing its work. After the loop, the function needs to write critical termination packets: ```c buffer[count++] = cpu_to_le32(PACKET3(PACKET3_PREAMBLE_CNTL, 0)); buffer[count++] = cpu_to_le32(PACKET3_PREAMBLE_END_CLEAR_STATE); buffer[count++] = cpu_to_le32(PACKET3(PACKET3_CLEAR_STATE, 0)); buffer[count++] = cpu_to_le32(0); ``` ### 2. **Meets Stable Tree Criteria** - **Small and contained**: Simple one-line removal with clear intent - **Low regression risk**: Removing early return allows proper completion - **Important bug fix**: Prevents GPU command buffer corruption - **No architectural changes**: Pure bug fix without new features ### 3. **Comparison with Historical Examples** Looking at the provided historical commits, this fix is similar to commit #3 (marked YES) which also fixed preamble handling. Both commits: - Fix logic bugs in AMD GPU driver - Have minimal code changes - Address proper command/state handling - Are critical for correct driver operation ### 4. **Stability Impact** While currently masked because all existing clear state data only uses `SECT_CONTEXT` sections, this bug creates: - **Buffer corruption risk**: Incomplete command buffers sent to GPU - **Forward compatibility issues**: Future hardware might use other section types - **Inconsistent state**: Size calculation function has same bug pattern ### 5. **Hardware Criticality** This affects the GFX9 generation which includes widely deployed GPUs like: - Vega series (RX Vega 56/64) - Raven Ridge APUs (Ryzen 2000G/3000G series) - Renoir APUs (Ryzen 4000 series) ### 6. **Clear Commit Message** The commit message explicitly states "We need to update the rest of the CSIB" - indicating this fixes incomplete processing, exactly what stable backports target. **Conclusion**: This is a textbook stable backport candidate - a small, contained fix for a clear logic bug in a critical GPU initialization path that could lead to hardware instability. The risk/reward ratio strongly favors backporting. drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c index 811cacacc2090..6cc382197378d 100644 --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c @@ -1782,8 +1782,6 @@ static void gfx_v9_0_get_csb_buffer(struct amdgpu_device *adev, PACKET3_SET_CONTEXT_REG_START); for (i = 0; i < ext->reg_count; i++) buffer[count++] = cpu_to_le32(ext->extent[i]); - } else { - return; } } } -- 2.39.5