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 046221B6CE3; Tue, 20 May 2025 16:22:07 +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=1747758128; cv=none; b=t7ACKP408ulTYaE7DAPZnrXKu+vMWPMcHLf75MuQ13CSeB7EV3C7V3ttvxgR9/Evv8IK1+/kVgl3fDvLYLLUEd9L8Smg2nZ7wBSfGFYmF2waJV8qUrV1S/FlhhSyE+MM2oSlWX7LMrcOJah7fef5ebrQJ9l3dNQnJ6KUVpU7Ikg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747758128; c=relaxed/simple; bh=PwfREHNjD08LoQHQb+2a+oNlUMWRFVPe7Pshx9/+Sd8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kPSWB7r1U+jV+NYb/MDxuk4tDQ5g/nxvMGEt4tLvUac3ucCIHSg+8d+8gcDOaYr11TOB9XLqhKdeSU9wj2ZuprArNg7/3fPQF4I6I8NX8/O4FDw+9TZlOpQKbK78RrVpGNq/E/sPpCYheHEJPauBCP+kEOrkDAI595slLJr/6gE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gS9PU2qF; 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="gS9PU2qF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00E5CC4CEE9; Tue, 20 May 2025 16:22:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747758127; bh=PwfREHNjD08LoQHQb+2a+oNlUMWRFVPe7Pshx9/+Sd8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gS9PU2qFMkHTyXBWHGpMjGBqnmICcI/5UxWYCsftTsMxQJZSbXiHsnyZTkAsmvodx PDnqBphspLZrY1SqdwpDyUyTKeQR1TO/3tFW9tvS2+lG4vQY0Ov7pSCuVolxAVrTPi mi/07FRg6VDuihqB85ocMl3Uo+09+GJd7NNeMFvd3SfFIx3riM4iSyXPAZEoYDUmgt 91SteDzb6V0ab6zijrraG+XA0Z01RAbS1eb7rEFFkPKUxmd2dNrqFvul0liYWaKYNl gU5oNX85u7X/IJ9zNNjfeNGI8Igl1eqicTPUnEDc6w6bsZ53DLqQFCMNVM9KWzA8e5 mDoNeqPHaWbdA== Date: Tue, 20 May 2025 18:22:02 +0200 From: Danilo Krummrich To: Rob Clark Cc: dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, Connor Abbott , Rob Clark , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , open list Subject: Re: [PATCH v5 02/40] drm/gpuvm: Allow VAs to hold soft reference to BOs Message-ID: References: <20250519175348.11924-1-robdclark@gmail.com> <20250519175348.11924-3-robdclark@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, May 20, 2025 at 08:54:53AM -0700, Rob Clark wrote: > On Tue, May 20, 2025 at 12:40 AM Danilo Krummrich wrote: > > On Mon, May 19, 2025 at 10:51:25AM -0700, Rob Clark wrote: > > It invalidates the whole design and makes a lot of functions fundamentally > > invalid to call, which is well demonstrated by all the WARN_ON() calls this > > patch attempts to add. > > I think of it more as adding a different mode of operation. One > where, perhaps some functions of gpuvm are not available, but that is > fine because they are also unneeded in that mode of operation. Hence > the WARN_ON()s to make that clear. This isn't a different mode of operation. You're breaking the design and internal guarantees and validity the code relies on. And as a consequence you have to disable the functions that are obviously broken by scattering it with WARN_ON() calls. And for the remaining code that is not disabled we'd have entirely new requirements on the guarantees the caller must provide in terms of reference counts. This is as if I'd try to promote a car with a broken engine control unit and would tell you "It's just in a different mode of operation, where driving isn't supported, but you can still heat the cabin and power the radio with the engine.", hoping that the broken engine control unit has no other side effects. Sorry, as much as I'd like to help and unblock you, I don't buy it.