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 1EB2DC433F5 for ; Fri, 25 Mar 2022 02:13:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241252AbiCYCPC (ORCPT ); Thu, 24 Mar 2022 22:15:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232634AbiCYCPC (ORCPT ); Thu, 24 Mar 2022 22:15:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45791381AB; Thu, 24 Mar 2022 19:13:28 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 61F3661838; Fri, 25 Mar 2022 02:13:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3CF0C340EC; Fri, 25 Mar 2022 02:13:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1648174407; bh=KSmv2W04ESy8xjgxw9/zdilquFr90HllFqmRQJ3P4ME=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PZop9NZQCVfT4DS8ZOGW6FvqAw8xX+rgnSDQDrhjj1XVb7BkZ/NoQYB/sSwRwkGhb XNiD0qXrJyQ9gUF8VZ7g06ONQ+8GF4OA34Pk7bSFavSOYbsm9Jz3GhpykdUDchaOH2 XCnOEy+80Yp6SO8o+9ZRNX3twEYn8MyrQfXtZK7FeaaljHjS36Gy4St3C8JpAjT6MS /B2yxCsFFz7enyrDeCbPTDRGsk2sDWUdy+Ep4V3AFVKnkgd8dgWOpfd84rwy6bmkhy mqSng19XSV3KRBS8NuzY4JL70MI6w/To5dWiZBcVU+7H16v239QbEzVEdubQwQ7dwx IIXxkap9yz7+g== Date: Fri, 25 Mar 2022 04:14:30 +0200 From: Jarkko Sakkinen To: Michael =?iso-8859-1?Q?Niew=F6hner?= Cc: Lino Sanfilippo , peterhuewe@gmx.de, jgg@ziepe.ca, stefanb@linux.vnet.ibm.com, stefanb@linux.ibm.com, James.Bottomley@hansenpartnership.com, keescook@chromium.org, jsnitsel@redhat.com, ml.linux@elloe.vision, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, twawrzynczak@chromium.org Subject: Re: [PATCH v3 0/4] Fixes for TPM interrupt handling Message-ID: References: <20210501135727.17747-1-LinoSanfilippo@gmx.de> <20210501135727.17747-3-LinoSanfilippo@gmx.de> <6722bf6f-1a3f-ee9c-55e2-cf63c64266a9@gmx.de> <2a1a1cf61732eff1608aeae74054a0c135c1671f.camel@mniewoehner.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2a1a1cf61732eff1608aeae74054a0c135c1671f.camel@mniewoehner.de> Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Thu, Mar 24, 2022 at 06:04:23PM +0100, Michael Niewöhner wrote: > Hi guys, > > On Thu, 2021-05-06 at 04:47 +0300, Jarkko Sakkinen wrote: > > On Wed, May 05, 2021 at 01:15:29AM +0200, Lino Sanfilippo wrote: > > > Hi, > > > > > > On 03.05.21 at 17:50, Jarkko Sakkinen wrote: > > > > What the heck is "simplification" and what that has to do with fixing > > > > anything? I don't understand your terminology. > > > > > > > > > The intention for this patch is not to fix anything. Please read the cover > > > letter and the commit message. > > > This patch is about making the locality handling easier by not > > > claiming/releasing > > > it multiple times over the driver life time, but claiming it once at driver > > > startup and only releasing it at driver shutdown. > > > > > > Right now we have locality request/release combos in > > > > > > - probe_itpm() > > > - tpm_tis_gen_interrupt() > > > - tpm_tis_core_init() > > > - tpm_chip_start() > > > > > > and there is still one combo missing for > > > > > > - tpm2_get_timeouts() > > > > > > which is the reason why we get the "TPM returned invalid status" bug in case > > > of TPM2 (and this is the bug which is _incidentally_ fixed by this patch, > > > see > > > below). > > > > > > And if we are going to enable interrupts, we have to introduce yet another > > > combo, > > > for accessing the status register in the interrupt handler, since TPM 2.0 > > > requires holding the locality for writing to the status register. That makes > > > 6 different code places in which we take and release the locality. > > > > > > With this patch applied we only take the locality at one place. Furthermore > > > with interrupts enabled we dont have to claim the locality for each handler > > > execution, saving us countless claim/release combinations at runtime. > > > > > > Hence the term "simplification" which is perfectly justified IMO. > > > > > > So again, this patch is "only" in preparation for the next patch when > > > interrupts > > > are actually enabled and we would have to take the locality in the interrupt > > > handler without this patch. > > > > So: what problem this patch does solve? > > > > /Jarkko > > > > first, thank you very much, Lino, for working on this! I've been debugging > issues with the tis driver in the last days and was about to start with the same > approach as yours when I luckily discovered your patch! > > Jarkko, while I agree, that the commit message is not optimal, Lino tried hard > to explain what the problems with the current code are and how they are / can be > fixed. Further, I too don't see why simplification / optimization is such a bad > thing. This driver is actually a very good example. I had a hard time, too, > figuring out what's going on there. A clean rewrite is a very valid approach > here IMO. It's not "polishing for nothing", as you described it, but actually > solving problems. > > Interrupt detection is broken for years now and finally a volunteer worked on a > solution. Don't you think this should be valued? Let's get this problem sorted > out :-) > > Lino, I'd be happy to test the patches, when you have time and interest to work > on this again! > > Thanks, Michael It's quite easy to test them out. Both fixes are in the mainline GIT tree. E.g. give a shot rc1, and please report if any issues persists to: linux-integrity@vger.kernel.org BR, Jarkko