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=-14.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 EAF3FC4338F for ; Thu, 29 Jul 2021 09:55:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2B9161052 for ; Thu, 29 Jul 2021 09:55:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235648AbhG2Jzh (ORCPT ); Thu, 29 Jul 2021 05:55:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:51386 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231488AbhG2Jzg (ORCPT ); Thu, 29 Jul 2021 05:55:36 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (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 9BC15600D1; Thu, 29 Jul 2021 09:55:33 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1m92lH-001iVA-Pl; Thu, 29 Jul 2021 10:55:31 +0100 Date: Thu, 29 Jul 2021 10:55:31 +0100 Message-ID: <87mtq5a1gs.wl-maz@kernel.org> From: Marc Zyngier To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, anshuman.khandual@arm.com, will@kernel.org, catalin.marinas@arm.com, james.morse@arm.com, mathieu.poirier@linaro.org, mike.leach@linaro.org, leo.yan@linaro.org, mark.rutland@arm.com Subject: Re: [PATCH 10/10] arm64: errata: Add workaround for TSB flush failures In-Reply-To: <20210728135217.591173-11-suzuki.poulose@arm.com> References: <20210728135217.591173-1-suzuki.poulose@arm.com> <20210728135217.591173-11-suzuki.poulose@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, anshuman.khandual@arm.com, will@kernel.org, catalin.marinas@arm.com, james.morse@arm.com, mathieu.poirier@linaro.org, mike.leach@linaro.org, leo.yan@linaro.org, mark.rutland@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 28 Jul 2021 14:52:17 +0100, Suzuki K Poulose wrote: > > Arm Neoverse-N2 (#2067961) and Cortex-A710 (#2054223) suffers > from errata, where a TSB (trace synchronization barrier) > fails to flush the trace data completely, when executed from > a trace prohibited region. In Linux we always execute it > after we have moved the PE to trace prohibited region. So, > we can apply the workaround everytime a TSB is executed. > > The work around is to issue two TSB consecutively. > > NOTE: This errata is defined as LOCAL_CPU_ERRATUM, implying > that a late CPU could be blocked from booting if it is the > first CPU that requires the workaround. This is because we > do not allow setting a cpu_hwcaps after the SMP boot. The > other alternative is to use "this_cpu_has_cap()" instead > of the faster system wide check, which may be a bit of an > overhead, given we may have to do this in nvhe KVM host > before a guest entry. > > Cc: Will Deacon > Cc: Catalin Marinas > Cc: Mathieu Poirier > Cc: Mike Leach > Cc: Mark Rutland > Cc: Anshuman Khandual > Cc: Marc Zyngier > Signed-off-by: Suzuki K Poulose > --- > Documentation/arm64/silicon-errata.rst | 4 ++++ > arch/arm64/Kconfig | 31 ++++++++++++++++++++++++++ > arch/arm64/include/asm/barrier.h | 17 +++++++++++++- > arch/arm64/kernel/cpu_errata.c | 19 ++++++++++++++++ > arch/arm64/tools/cpucaps | 1 + > 5 files changed, 71 insertions(+), 1 deletion(-) [...] > diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h > index 451e11e5fd23..3bc1ed436e04 100644 > --- a/arch/arm64/include/asm/barrier.h > +++ b/arch/arm64/include/asm/barrier.h > @@ -23,7 +23,7 @@ > #define dsb(opt) asm volatile("dsb " #opt : : : "memory") > > #define psb_csync() asm volatile("hint #17" : : : "memory") > -#define tsb_csync() asm volatile("hint #18" : : : "memory") > +#define __tsb_csync() asm volatile("hint #18" : : : "memory") > #define csdb() asm volatile("hint #20" : : : "memory") > > #ifdef CONFIG_ARM64_PSEUDO_NMI > @@ -46,6 +46,21 @@ > #define dma_rmb() dmb(oshld) > #define dma_wmb() dmb(oshst) > > + > +#define tsb_csync() \ > + do { \ > + /* \ > + * CPUs affected by Arm Erratum 2054223 or 2067961 needs \ > + * another TSB to ensure the trace is flushed. \ > + */ \ > + if (cpus_have_const_cap(ARM64_WORKAROUND_TSB_FLUSH_FAILURE)) { \ Could this be made a final cap instead? Or do you expect this to be usable before caps have been finalised? > + __tsb_csync(); \ > + __tsb_csync(); \ > + } else { \ > + __tsb_csync(); \ > + } \ nit: You could keep one unconditional __tsb_csync(). Thanks, M. -- Without deviation from the norm, progress is not possible.