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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD06EC47253 for ; Thu, 6 Aug 2020 11:04:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD667204FD for ; Thu, 6 Aug 2020 11:04:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="nYcGaQwW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728276AbgHFG6G (ORCPT ); Thu, 6 Aug 2020 02:58:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727028AbgHFG6G (ORCPT ); Thu, 6 Aug 2020 02:58:06 -0400 Received: from mail-lj1-x242.google.com (mail-lj1-x242.google.com [IPv6:2a00:1450:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B418CC061574 for ; Wed, 5 Aug 2020 23:58:05 -0700 (PDT) Received: by mail-lj1-x242.google.com with SMTP id v9so16046324ljk.6 for ; Wed, 05 Aug 2020 23:58:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=jiAxdAhy44xI/+/AQRE2sQVzFABr4tFigqxJ0w++SSo=; b=nYcGaQwWN1KvEfOh4V6Jk2qsZY4XCn6wman7fkG3z+0B7GJCJTcA3vBNG+3Yh+o5Xf z99N+ftBbHJWfKRr0XllP6Ve+NhlWoUY7Y5DvHnR/x2M+UxGaCzesVXNyqoin93iDDDS Rwfi/q+ib0ySA60qFdU230/FYojWzM6Aoh2Jp+UwWT+mqoq6AUeUet30E8NAC26vYvsY LAdg4Zcy8ZZF0S3lN7HUNF9NXfKfVdNk8/RIZd2leW2aBwzeaITX5I0HFDCRBVBP/Zuq RVEDqcI3auDGxBNe8k7YtDFltpqq6CCesyLoPpeK3NVrHA765V8GULuHP5UrMZkuI/Dx 1PfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=jiAxdAhy44xI/+/AQRE2sQVzFABr4tFigqxJ0w++SSo=; b=CWSluyfe6QqP9znvGWGb28Sau5X79UBTZByuITzVRR/5Dwg14yMpuOJYh8xf3loiex 8yuOwD6yUqbsu0tYuBPVfYshys4OHHXPN9IVv8cmCTPS/pEwxrdqbCvTXtS95WHO01Zc izYoEJwsJ7ld0LcwVw8RaOG2RDOZIlzmh7OfabSrGY5oPyuSuWLnrmtPgoBDhnEy8dly c8xJ5KVidSuil9a2IKYL/dCXXR9pES1fLMu/7KeCQSXUMv9fsuoHD2U9k3KbIl+Mv61K vo7W9wrVu6Ehn3/Oln/dd6Inlis1nA+RpnwRposHqb5Bxxh1ThnnjMhJhsDeMAEnpkdB aAWA== X-Gm-Message-State: AOAM531SbPd03zQkR1j34frz1ssVc/lKBgDbuRyDuCrf6mQN2H28/3Sj +H14UG7ftTiSt0iNMOIkiEHhu53G0zXEcVVx6HdD8w== X-Google-Smtp-Source: ABdhPJx9YdSrUhOSQ2Hd+9Yu4GVO5UeOPj2Yoo3fdfaZao5Jo1szgUE+Vj+/jfz+mPlWrxoD0SoNbXY7XooJO9Hz1gg= X-Received: by 2002:a05:651c:1293:: with SMTP id 19mr2954610ljc.427.1596697084120; Wed, 05 Aug 2020 23:58:04 -0700 (PDT) MIME-Version: 1.0 References: <20200723084622.31134-1-jorge@foundries.io> <20200723084622.31134-2-jorge@foundries.io> <20200724142305.GA24164@trex> <20200805203817.GA12229@trex> <20200806063040.GA27943@trex> In-Reply-To: <20200806063040.GA27943@trex> From: Sumit Garg Date: Thu, 6 Aug 2020 12:27:51 +0530 Message-ID: Subject: Re: [PATCHv2 2/2] hwrng: optee: fix wait use case To: "Jorge Ramirez-Ortiz, Foundries" Cc: Matt Mackall , Herbert Xu , Jens Wiklander , Arnd Bergmann , ricardo@foundries.io, Michael Scott , Greg Kroah-Hartman , op-tee@lists.trustedfirmware.org, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Thu, 6 Aug 2020 at 12:00, Jorge Ramirez-Ortiz, Foundries wrote: > > On 06/08/20, Sumit Garg wrote: > > On Thu, 6 Aug 2020 at 02:08, Jorge Ramirez-Ortiz, Foundries > > wrote: > > > > > > On 05/08/20, Sumit Garg wrote: > > > > Apologies for my delayed response as I was busy with some other tas= ks > > > > along with holidays. > > > > > > no pb! was just making sure this wasnt falling through some cracks. > > > > > > > > > > > On Fri, 24 Jul 2020 at 19:53, Jorge Ramirez-Ortiz, Foundries > > > > wrote: > > > > > > > > > > On 24/07/20, Sumit Garg wrote: > > > > > > On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz wrote: > > > > > > > > > > > > > > The current code waits for data to be available before attemp= ting a > > > > > > > second read. However the second read would not be executed as= the > > > > > > > while loop exits. > > > > > > > > > > > > > > This fix does not wait if all data has been read and reads a = second > > > > > > > time if only partial data was retrieved on the first read. > > > > > > > > > > > > > > This fix also does not attempt to read if not data is request= ed. > > > > > > > > > > > > I am not sure how this is possible, can you elaborate? > > > > > > > > > > currently, if the user sets max 0, get_optee_rng_data will regard= less > > > > > issuese a call to the secure world requesting 0 bytes from the RN= G > > > > > > > > > > > > > This case is already handled by core API: rng_dev_read(). > > > > > > ah ok good point, you are right > > > but yeah, there is no consequence to the actual patch. > > > > > > > So, at least you could get rid of the corresponding text from commit me= ssage. > > > > > > > > > > > with this patch, this request is avoided. > > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Jorge Ramirez-Ortiz > > > > > > > --- > > > > > > > v2: tidy up the while loop to avoid reading when no data is = requested > > > > > > > > > > > > > > drivers/char/hw_random/optee-rng.c | 4 ++-- > > > > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > > > > > > > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/cha= r/hw_random/optee-rng.c > > > > > > > index 5bc4700c4dae..a99d82949981 100644 > > > > > > > --- a/drivers/char/hw_random/optee-rng.c > > > > > > > +++ b/drivers/char/hw_random/optee-rng.c > > > > > > > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng = *rng, void *buf, size_t max, bool wait) > > > > > > > if (max > MAX_ENTROPY_REQ_SZ) > > > > > > > max =3D MAX_ENTROPY_REQ_SZ; > > > > > > > > > > > > > > - while (read =3D=3D 0) { > > > > > > > + while (read < max) { > > > > > > > rng_size =3D get_optee_rng_data(pvt_data, dat= a, (max - read)); > > > > > > > > > > > > > > data +=3D rng_size; > > > > > > > read +=3D rng_size; > > > > > > > > > > > > > > if (wait && pvt_data->data_rate) { > > > > > > > - if (timeout-- =3D=3D 0) > > > > > > > + if ((timeout-- =3D=3D 0) || (read =3D= =3D max)) > > > > > > > > > > > > If read =3D=3D max, would there be any sleep? > > > > > > > > > > no but I see no reason why there should be a wait since we alread= y have > > > > > all the data that we need; the msleep is only required when we ne= ed to > > > > > wait for the RNG to generate entropy for the number of bytes we a= re > > > > > requesting. if we are requesting 0 bytes, the entropy is already > > > > > available. at leat this is what makes sense to me. > > > > > > > > > > > > > Wouldn't it lead to a call as msleep(0); that means no wait as well= ? > > > > > > I dont understand: there is no reason to wait if read =3D=3D max and = this > > > patch will not wait: if read =3D=3D max it calls 'return read' > > > > > > am I misunderstanding your point? > > > > What I mean is that we shouldn't require this extra check here as > > there wasn't any wait if read =3D=3D max with existing implementation t= oo. > > um, I am getting confused Sumit > > with the exisiting implementation (the one we aim to replace), if get_opt= ee_rng_data reads all the values requested on the first call (ie, read =3D = 0) with wait set to true, the call will wait with msleep(0). Which is unnec= essary and waits for a jiffy (ie, the call to msleep 0 will schedule a one = jiffy timeout interrruptible) > > with this alternative implementation, msleep(0) does not get called. > > are we in synch? Ah, I see msleep(0) also by default schedules timeout for 1 jiffy. So we are in sync now. Probably you can clarify this in commit message as well to avoid confusion. -Sumit > > > > > -Sumit > > > > > > > > > > > > > -Sumit > > > > > > > > > > > > > > > > > > > > > -Sumit > > > > > > > > > > > > > return read; > > > > > > > msleep((1000 * (max - read)) / pvt_da= ta->data_rate); > > > > > > > } else { > > > > > > > -- > > > > > > > 2.17.1 > > > > > > >