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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 6D2B5C64E7D for ; Sun, 29 Nov 2020 03:20:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1841D20825 for ; Sun, 29 Nov 2020 03:20:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="msK2tFih" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726781AbgK2DTp (ORCPT ); Sat, 28 Nov 2020 22:19:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:42624 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726635AbgK2DTp (ORCPT ); Sat, 28 Nov 2020 22:19:45 -0500 Received: from kernel.org (83-245-197-237.elisa-laajakaista.fi [83.245.197.237]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 41EF5206CB; Sun, 29 Nov 2020 03:19:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606619943; bh=pbRFxDArwnCUPLUu+gm70WqV0swkIAzhjUz7Jp3Uybs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=msK2tFihoSFUEIZt2fDS/vBnWZH3cS/bev+RgqwZXSy1bTF5k19bcs5aK57FnmlmW g+HDBn4fGID5bSxgs6agjj8E8goyhASV1E1LjrUhEw7Y/hGFF3RfzX0H/NU8U6cFnx b5QHZsKmpIXwe411uoCyNkFdQvYB0xZNlQZCXQc8= Date: Sun, 29 Nov 2020 05:18:58 +0200 From: Jarkko Sakkinen To: Jerry Snitselaar Cc: Matthew Garrett , linux-integrity , Linux Kernel Mailing List , Peter Huewe , Jason Gunthorpe , Hans de Goede , James Bottomley Subject: Re: [PATCH] tpm_tis: Disable interrupts on ThinkPad T490s Message-ID: <20201129031858.GB39488@kernel.org> References: <20201015214430.17937-1-jsnitsel@redhat.com> <87d009c0pn.fsf@redhat.com> <20201124032623.GA40007@kernel.org> <871rgiod53.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <871rgiod53.fsf@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 24, 2020 at 10:52:56AM -0700, Jerry Snitselaar wrote: > > Jarkko Sakkinen @ 2020-11-23 20:26 MST: > > > On Wed, Nov 18, 2020 at 11:36:20PM -0700, Jerry Snitselaar wrote: > >> > >> Matthew Garrett @ 2020-10-15 15:39 MST: > >> > >> > On Thu, Oct 15, 2020 at 2:44 PM Jerry Snitselaar wrote: > >> >> > >> >> There is a misconfiguration in the bios of the gpio pin used for the > >> >> interrupt in the T490s. When interrupts are enabled in the tpm_tis > >> >> driver code this results in an interrupt storm. This was initially > >> >> reported when we attempted to enable the interrupt code in the tpm_tis > >> >> driver, which previously wasn't setting a flag to enable it. Due to > >> >> the reports of the interrupt storm that code was reverted and we went back > >> >> to polling instead of using interrupts. Now that we know the T490s problem > >> >> is a firmware issue, add code to check if the system is a T490s and > >> >> disable interrupts if that is the case. This will allow us to enable > >> >> interrupts for everyone else. If the user has a fixed bios they can > >> >> force the enabling of interrupts with tpm_tis.interrupts=1 on the > >> >> kernel command line. > >> > > >> > I think an implication of this is that systems haven't been > >> > well-tested with interrupts enabled. In general when we've found a > >> > firmware issue in one place it ends up happening elsewhere as well, so > >> > it wouldn't surprise me if there are other machines that will also be > >> > unhappy with interrupts enabled. Would it be possible to automatically > >> > detect this case (eg, if we get more than a certain number of > >> > interrupts in a certain timeframe immediately after enabling the > >> > interrupt) and automatically fall back to polling in that case? It > >> > would also mean that users with fixed firmware wouldn't need to pass a > >> > parameter. > >> > >> I believe Matthew is correct here. I found another system today > >> with completely different vendor for both the system and the tpm chip. > >> In addition another Lenovo model, the L490, has the issue. > >> > >> This initial attempt at a solution like Matthew suggested works on > >> the system I found today, but I imagine it is all sorts of wrong. > >> In the 2 systems where I've seen it, there are about 100000 interrupts > >> in around 1.5 seconds, and then the irq code shuts down the interrupt > >> because they aren't being handled. > >> > >> > >> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c > >> index 49ae09ac604f..478e9d02a3fa 100644 > >> --- a/drivers/char/tpm/tpm_tis_core.c > >> +++ b/drivers/char/tpm/tpm_tis_core.c > >> @@ -27,6 +27,11 @@ > >> #include "tpm.h" > >> #include "tpm_tis_core.h" > >> > >> +static unsigned int time_start = 0; > >> +static bool storm_check = true; > >> +static bool storm_killed = false; > >> +static u32 irqs_fired = 0; > > > > Maybe kstat_irqs() would be a better idea than ad hoc stats. > > > > Thanks, yes that would be better. > > >> + > >> static void tpm_tis_clkrun_enable(struct tpm_chip *chip, bool value); > >> > >> static void tpm_tis_enable_interrupt(struct tpm_chip *chip, u8 mask) > >> @@ -464,25 +469,31 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len) > >> return rc; > >> } > >> > >> -static void disable_interrupts(struct tpm_chip *chip) > >> +static void __disable_interrupts(struct tpm_chip *chip) > >> { > >> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev); > >> u32 intmask; > >> int rc; > >> > >> - if (priv->irq == 0) > >> - return; > >> - > >> rc = tpm_tis_read32(priv, TPM_INT_ENABLE(priv->locality), &intmask); > >> if (rc < 0) > >> intmask = 0; > >> > >> intmask &= ~TPM_GLOBAL_INT_ENABLE; > >> rc = tpm_tis_write32(priv, TPM_INT_ENABLE(priv->locality), intmask); > >> + chip->flags &= ~TPM_CHIP_FLAG_IRQ; > >> +} > >> + > >> +static void disable_interrupts(struct tpm_chip *chip) > >> +{ > >> + struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev); > >> > >> + if (priv->irq == 0) > >> + return; > >> + > >> + __disable_interrupts(chip); > >> devm_free_irq(chip->dev.parent, priv->irq, chip); > >> priv->irq = 0; > >> - chip->flags &= ~TPM_CHIP_FLAG_IRQ; > >> } > >> > >> /* > >> @@ -528,6 +539,12 @@ static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len) > >> int rc, irq; > >> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev); > >> > >> + if (unlikely(storm_killed)) { > >> + devm_free_irq(chip->dev.parent, priv->irq, chip); > >> + priv->irq = 0; > >> + storm_killed = false; > >> + } > > > > OK this kind of bad solution because if tpm_tis_send() is not called, > > then IRQ is never freed. AFAIK, devres_* do not sleep but use spin > > lock, i.e. you could render out both storm_check and storm_killed. > > > > Is there a way to flag it for freeing later while in an interrupt > context? I'm not sure where to clean it up since devm_free_irq can't be > called in tis_int_handler. > > Before diving further into that though, does anyone else have an opinion > on ripping out the irq code, and just using polling? We've been only > polling since 2015 anyways. Given these all these issues, it's quite obvious that Windows side is just polling. I'll ack a patch that removes the IRQ code for sure. /Jarkko