From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (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 6E9B720C008; Thu, 13 Feb 2025 08:36:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739435767; cv=none; b=gjykiplFykkZcd4u4Kb6xN5VtpICidq+aQDWpkKhQ9kWxrOtXXeF+T69/NGdcA1grE7X5NWto43t8/jnigRy7DUpvZxsyKPgSZJ4NiltLkeHpcgAHRBBMkwR5YcWIdXvPcst6yMbrvfRmQWqq5bUWTLfac2PcGIgF/dhho+5fJA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739435767; c=relaxed/simple; bh=0ljVmsCU5Z5rev84vqt4fS5crKIkLIWMPKtmSDok3Cg=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=X+nriegd3bIeRw1NQtrENpsHmD3OxMSSD/qBNMYyueTw1FG5ur8mbFdNY8Dyv/ZExbDM0i2KpQfb4k+OoYhlkDDtgsTzzsm+l81QrzFF/jGgo/v9Oq4hRE2COp+Df95fyxqLQ0qJVmcPUPy3Do+vXl7ePynZLNN83daXYBn7HoI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=RZNzLEyW; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="RZNzLEyW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1739435763; bh=0ljVmsCU5Z5rev84vqt4fS5crKIkLIWMPKtmSDok3Cg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=RZNzLEyW5od4bpV21W2GOLaB+EQf9NM3Vr/28YMK8Y3zqoCs/o8noc4abjJup+69D h+CtGYYRujty8aJDL3vRiUwVdW1tB7UqrBGkQQjkAJSNqGufNsHtsV+p5eRSIrhwXA 5yU74D7snI9/gkHWlPM1XKv+X/lzlHZP+b8sIOrJzF1nUPCNY9xXA2rCd6GxHxhbTX QXJj16DbEu5wehPijt0JmwzwJ42ROjvMo1lijGkdXdl5Nm7Igju1Mc+VhbE9ej2DLL 8FBAnNGeigkOXtznT1AUSH1ycFYkWmPnzRcUf6bd3BI9w9WuP/Pa1fyt3AUEbk9tSW P8r0QvjF/v22g== Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 7D15417E0F44; Thu, 13 Feb 2025 09:36:02 +0100 (CET) Date: Thu, 13 Feb 2025 09:35:57 +0100 From: Boris Brezillon To: Sumit Garg Cc: Jens Wiklander , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, op-tee@lists.trustedfirmware.org, linux-arm-kernel@lists.infradead.org, Olivier Masse , Thierry Reding , Yong Wu , Sumit Semwal , Benjamin Gaignard , Brian Starkey , John Stultz , "T . J . Mercier" , Christian =?UTF-8?B?S8O2bmln?= , Matthias Brugger , AngeloGioacchino Del Regno , azarrabi@qti.qualcomm.com, Florent Tomasin Subject: Re: [PATCH v4 0/6] TEE subsystem for restricted dma-buf allocations Message-ID: <20250213093557.278f5d19@collabora.com> In-Reply-To: References: <20241217100809.3962439-1-jens.wiklander@linaro.org> <20250212205613.4400a888@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 13 Feb 2025 12:11:52 +0530 Sumit Garg wrote: > Hi Boris, > > On Thu, 13 Feb 2025 at 01:26, Boris Brezillon > wrote: > > > > +Florent, who's working on protected-mode support in Panthor. > > > > Hi Jens, > > > > On Tue, 17 Dec 2024 11:07:36 +0100 > > Jens Wiklander wrote: > > > > > Hi, > > > > > > This patch set allocates the restricted DMA-bufs via the TEE subsystem. > > > > We're currently working on protected-mode support for Panthor [1] and it > > looks like your series (and the OP-TEE implementation that goes with > > it) would allow us to have a fully upstream/open solution for the > > protected content use case we're trying to support. I need a bit more > > time to play with the implementation but this looks very promising > > (especially the lend rstmem feature, which might help us allocate our > > FW sections that are supposed to execute code accessing protected > > content). > > Glad to hear that, if you can demonstrate an open source use case > based on this series then it will help to land it. We really would > love to see support for restricted DMA-buf consumers be it GPU, crypto > accelerator, media pipeline etc. > > > > > > > > > The TEE subsystem handles the DMA-buf allocations since it is the TEE > > > (OP-TEE, AMD-TEE, TS-TEE, or perhaps a future QCOMTEE) which sets up the > > > restrictions for the memory used for the DMA-bufs. > > > > > > I've added a new IOCTL, TEE_IOC_RSTMEM_ALLOC, to allocate the restricted > > > DMA-bufs. This IOCTL reaches the backend TEE driver, allowing it to choose > > > how to allocate the restricted physical memory. > > > > I'll probably have more questions soon, but here's one to start: any > > particular reason you didn't go for a dma-heap to expose restricted > > buffer allocation to userspace? I see you already have a cdev you can > > take ioctl()s from, but my understanding was that dma-heap was the > > standard solution for these device-agnostic/central allocators. > > This series started with the DMA heap approach only here [1] but later > discussions [2] lead us here. To point out specifically: > > - DMA heaps require reliance on DT to discover static restricted > regions carve-outs whereas via the TEE implementation driver (eg. > OP-TEE) those can be discovered dynamically. Hm, the system heap [1] doesn't rely on any DT information AFAICT. The dynamic allocation scheme, where the TEE implementation allocates a chunk of protected memory for us would have a similar behavior, I guess. > - Dynamic allocation of buffers and making them restricted requires > vendor specific driver hooks with DMA heaps whereas the TEE subsystem > abstracts that out with underlying TEE implementation (eg. OP-TEE) > managing the dynamic buffer restriction. Yeah, the lend rstmem feature is clearly something tee specific, and I think that's okay to assume the user knows the protection request should go through the tee subsystem in that case. > - TEE subsystem already has a well defined user-space interface for > managing shared memory buffers with TEE and restricted DMA buffers > will be yet another interface managed along similar lines. Okay, so the very reason I'm asking about the dma-buf heap interface is because there might be cases where the protected/restricted allocation doesn't go through the TEE (Mediatek has a TEE-free implementation for instance, but I realize vendor implementations are probably not the best selling point :-/). If we expose things as a dma-heap, we have a solution where integrators can pick the dma-heap they think is relevant for protected buffer allocations without the various drivers (GPU, video codec, ...) having to implement a dispatch function for all possible implementations. The same goes for userspace allocations, where passing a dma-heap name, is simpler than supporting different ioctl()s based on the allocation backend. [1]https://elixir.bootlin.com/linux/v6.13.2/source/drivers/dma-buf/heaps/system_heap.c#L424