From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A95EC001B2 for ; Fri, 16 Dec 2022 05:10:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229783AbiLPFKA (ORCPT ); Fri, 16 Dec 2022 00:10:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229504AbiLPFJ5 (ORCPT ); Fri, 16 Dec 2022 00:09:57 -0500 Received: from mail-vk1-xa32.google.com (mail-vk1-xa32.google.com [IPv6:2607:f8b0:4864:20::a32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A46B49B5B for ; Thu, 15 Dec 2022 21:09:56 -0800 (PST) Received: by mail-vk1-xa32.google.com with SMTP id z23so642350vkb.12 for ; Thu, 15 Dec 2022 21:09:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=Sgu7X5BHX9sTfJbpXF2aHjOSGbnmcd7dkZy4Cb0etJk=; b=M1w027DTaUSOaUT+L0Q2TD5xvofS9C+uRrhU6fy9jmJTJ5XKICEYETUFU7LCyVvJA6 ZQuO4aVw7Q00TnyOzLx0vBWJhGbWOADFrkWM4miPXND6LquO5OlLRjYgB9RhC7q9MQ/Y EPb7anG9uNw51P/mZVpFfY5s05mI73Aj4v2luZFlLfuGaX1Xk0s/mcP5+XI2tQRd3fKs XdvPXlZll9xO/MZD/p9PJ+vnz+9n/Dpcl3gRe2RHBqLRvtlqKphWHPRO0gHbGYW3updE ZY89H7SFkuoU/pT37Z6+pYgT9jZYsM/7eMqO2DfMAdWtKeoMl8JZ7GY+TWM7qa33AI6H a0mw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Sgu7X5BHX9sTfJbpXF2aHjOSGbnmcd7dkZy4Cb0etJk=; b=q0dTmgwKI3Whh8SEz71wzx2RVcqZdb5tE9vLzWFKBmAj4lU/56rkOtuYo1nIkdkm38 uXfqATebc/e58iwyaUOmI8m63EKYscsg/YHcBCzhMdREFEZe3hbCPQidm+QzfxOG6r1K PgTMncxd4vAYsFTkltc0pE/12n/Qy96cf4pEENqOUz6fgJlugjFm3ICqF0Hi90AH0fKN 5/ZyxgoiLvrEOxPdscvtS0mnKbFFu79r+pKb2wecdcmZRCfGQJe2ygm279pnUWIoSdCY TGm6F6Xecjy/GXfmQzKY9LfSotns8mH3J0Lm0ut5Ae7UQTYYWB+USdaYGQLLIoTIcv50 tSKA== X-Gm-Message-State: ANoB5pkesU8pe7bh3gPqkDqV+FaZrZ7NgyVtqYObIPOSunBtrZy9ZOow gjMEPJZfkEvI8JLlLglleuWKe9jyLFRAMAwojwet8w== X-Google-Smtp-Source: AA0mqf4Tnqsv1nPsCoELHu7nULwdsh55iwL8noXBFP2vaVOSypvSridY498rb7ry9fMro1J8aFbQyed5l/AvCnPCAgg= X-Received: by 2002:a05:6122:41e:b0:3bd:ad7c:b3ec with SMTP id e30-20020a056122041e00b003bdad7cb3ecmr12932777vkd.0.1671167395589; Thu, 15 Dec 2022 21:09:55 -0800 (PST) MIME-Version: 1.0 References: <20221002002326.946620-1-ira.weiny@intel.com> <20221002002326.946620-3-ira.weiny@intel.com> In-Reply-To: From: Sumit Garg Date: Fri, 16 Dec 2022 10:39:44 +0530 Message-ID: Subject: Re: [PATCH 2/4] tee: Remove vmalloc page support To: Ira Weiny Cc: Jens Wiklander , Linus Torvalds , =?UTF-8?B?UGhpbCBDaGFuZyAo5by15LiW5YuzKQ==?= , Andrew Morton , Al Viro , "Fabio M. De Francesco" , Christoph Hellwig , "op-tee@lists.trustedfirmware.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 16 Dec 2022 at 06:11, Ira Weiny wrote: > > On Fri, Oct 07, 2022 at 10:12:57AM +0200, Jens Wiklander wrote: > > On Thu, Oct 6, 2022 at 8:20 PM Linus Torvalds > > wrote: > > > > > > On Wed, Oct 5, 2022 at 11:24 PM Sumit Garg wrote: > > > > > > > > Sorry but you need to get your driver mainline in order to support > > > > vmalloc interface. > > > > > > Actually, I think even then we shouldn't support vmalloc - and > > > register_shm_helper() just needs to be changed to pass in an array of > > > actual page pointers instead. > > > > register_shm_helper() is an internal function, I suppose it's what's > > passed to tee_shm_register_user_buf() and especially > > tee_shm_register_kernel_buf() in this case. > > > > So the gain is that in the kernel it becomes the caller's > > responsibility to provide the array of page pointers and the TEE > > subsystem doesn't need to care about what kind of kernel memory it is > > any longer. Yes, that should avoid eventual complexities with > > vmalloc() etc. > > I finally spent some time digging into this again. > > Overall I'm not opposed to trying to clean up the code more but I feel like the > removal of TEE_SHM_USER_MAPPED is too complex for the main goal; to remove a > caller of kmap_to_page(). > > Not only is that flag used in release_registered_pages() but it is also used in > tee_shm_fop_mmap(). I'm not following exactly why. I think this is to allow > mmap of the tee_shm's allocated by kernel users? No, its rather to allow mmap of tee_shm allocated via tee_shm_alloc_user_buf(). Have a look at its user-space usage here [1]. So overall I agree here that we can't get rid of TEE_SHM_USER_MAPPED completely as it has a valid mmap use-case. [1] https://github.com/OP-TEE/optee_client/blob/master/libteec/src/tee_client_api.c#L907 > Which I _think_ is > orthogonal to the callers of tee_shm_register_kernel_buf()? > > > > > > > > > At that point TEE_SHM_USER_MAPPED should also go away, because then > > > it's the caller that should just do either the user space page > > > pinning, or pass in the kernel page pointer. > > > > > > JensW, is there some reason that wouldn't work? > > > > We still need to know if it's kernel or user pages in > > release_registered_pages(). > > Yes. > > As I dug into this it seemed ok to define a tee_shm_kernel_free(). Pull out > the allocation of the page array from register_shm_helper() such that it could > be handled by tee_shm_register_kernel_buf() and this new tee_shm_kernel_free(). > +1 > This seems reasonable because the only callers of tee_shm_register_kernel_buf() > are in trusted_tee.c and they all call tee_shm_free() on the registered memory > prior to returning. > > Other callers[*] of tee_shm_free() obtained tee_shm from > tee_shm_alloc_kernel_buf() which AFAICT avoids all this nonsense. > > [*] such as .../drivers/firmware/broadcom/tee_bnxt_fw.c. > > > > > The struct tee_shm:s acquired with syscalls from user space are > > reference counted. As are the kernel tee_shm:s, but I believe we could > > separate them to avoid reference counting tee_shm:s used by kernel > > clients if needed. I'll need to look closer at this if we're going to > > use that approach. > > > > Without reference counting the caller of tee_shm_free() can be certain > > that the secure world is done with the memory so we could delegate the > > kernel pages part of release_registered_pages() to the caller instead. > > > > I'm not sure I follow you here. Would this be along the lines of creating a > tee_shm_free_kernel() to be used in trusted_tee.c for those specific kernel > data? I can't find a reason/use-case for the TEE subsystem to keep a refcount of memory registered by other kernel drivers like trusted_tee.c. So yes I think it should be safe to directly free that shm via tee_shm_free_kernel(). Also with that we can simplify shm registration by kernel clients via directly passing page pointers to tee_shm_register_kernel_buf() (I would rather rename this API as tee_shm_register_kernel_pages()). -Sumit > > Overall I feel like submitting this series again with Christoph and Al's > comments addressed is the best way forward to get rid of kmap_to_page(). I > would really like to get moving on that to avoid any further issues with the > kmap conversions. > > But if folks feel strongly enough about removing that flag I can certainly try > to do so. > > Ira > > > Cheers, > > Jens > > > > > > > > Linus