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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 0C3CBC433C1 for ; Wed, 24 Mar 2021 17:10:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA570619FB for ; Wed, 24 Mar 2021 17:10:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237310AbhCXRJj (ORCPT ); Wed, 24 Mar 2021 13:09:39 -0400 Received: from foss.arm.com ([217.140.110.172]:36750 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237559AbhCXRHC (ORCPT ); Wed, 24 Mar 2021 13:07:02 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7BE88ED1; Wed, 24 Mar 2021 10:07:01 -0700 (PDT) Received: from [10.57.51.32] (unknown [10.57.51.32]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E4B8D3F7D7; Wed, 24 Mar 2021 10:06:59 -0700 (PDT) Subject: Re: [PATCH v5 05/19] arm64: Add support for trace synchronization barrier To: Marc Zyngier Cc: Catalin Marinas , Mathieu Poirier , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, mike.leach@linaro.org, leo.yan@linaro.org, anshuman.khandual@arm.com, Will Deacon References: <20210323120647.454211-1-suzuki.poulose@arm.com> <20210323120647.454211-6-suzuki.poulose@arm.com> <20210323182142.GA16080@arm.com> <7675ab71-c2ff-91e0-5728-fcb216ac1e0d@arm.com> <875z1gk6fo.wl-maz@kernel.org> <1b5e5bb2-b89f-fa35-0a8b-8c5476cb9ff6@arm.com> <871rc4jzn0.wl-maz@kernel.org> <17e57b01-840b-dbeb-c09f-1c04becb8749@arm.com> <87tup0ikf0.wl-maz@kernel.org> From: Suzuki K Poulose Message-ID: <59aec851-e980-0a6d-8ba5-56a35fa5a7a9@arm.com> Date: Wed, 24 Mar 2021 17:06:58 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <87tup0ikf0.wl-maz@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/03/2021 16:30, Marc Zyngier wrote: > On Wed, 24 Mar 2021 16:25:12 +0000, > Suzuki K Poulose wrote: >> >> On 24/03/2021 16:16, Marc Zyngier wrote: >>> On Wed, 24 Mar 2021 15:51:14 +0000, >>> Suzuki K Poulose wrote: >>>> >>>> On 24/03/2021 13:49, Marc Zyngier wrote: >>>>> On Wed, 24 Mar 2021 09:39:13 +0000, >>>>> Suzuki K Poulose wrote: >>>>>> >>>>>> On 23/03/2021 18:21, Catalin Marinas wrote: >>>>>>> Hi Suzuki? >>>>>>> >>>>>>> On Tue, Mar 23, 2021 at 12:06:33PM +0000, Suzuki K Poulose wrote: >>>>>>>> tsb csync synchronizes the trace operation of instructions. >>>>>>>> The instruction is a nop when FEAT_TRF is not implemented. >>>>>>>> >>>>>>>> Cc: Mathieu Poirier >>>>>>>> Cc: Mike Leach >>>>>>>> Cc: Catalin Marinas >>>>>>>> Cc: Will Deacon >>>>>>>> Signed-off-by: Suzuki K Poulose >>>>>>> >>>>>>> How do you plan to merge these patches? If they go via the coresight >>>>>>> tree: >>>>>>> >>>>>> >>>>>> Ideally all of this should go via the CoreSight tree to have the >>>>>> dependencies solved at one place. But there are some issues : >>>>>> >>>>>> If this makes to 5.13 queue for CoreSight, >>>>>> >>>>>> 1) CoreSight next is based on rc2 at the moment and we have fixes gone >>>>>> into rc3 and later, which this series will depend on. (We could move >>>>>> the next tree forward to a later rc to solve this). >>>>>> >>>>>> 2) There could be conflicts with the kvmarm tree for the KVM host >>>>>> changes (That has dependency on the TRBE definitions patch). >>>>>> >>>>>> If it doesn't make to 5.13 queue, it would be good to have this patch, >>>>>> the TRBE defintions and the KVM host patches queued for 5.13 (not sure >>>>>> if this is acceptable) and we could rebase the CoreSight changes on 5.13 >>>>>> and push it to next release. >>>>>> >>>>>> I am open for other suggestions. >>>>>> >>>>>> Marc, Mathieu, >>>>>> >>>>>> Thoughts ? >>>>> >>>>> I was planning to take the first two patches in 5.12 as fixes (they >>>>> are queued already, and would hopefully land in -rc5). If that doesn't >>>>> fit with the plan, please let me know ASAP. >>>> >>>> Marc, >>>> >>>> I think it would be better to hold on pushing those patches until we >>>> have a clarity on how things will go. >>> >>> OK. I thought there was a need for these patches to prevent guest >>> access to the v8.4 self hosted tracing feature that went in 5.12 >>> though[1]... Did I get it wrong? >> >> Yes, that is correct. The guest could access the Trace Filter Control >> register and fiddle with the host settings, without this patch. >> e.g, it could disable tracing at EL0/EL1, without the host being >> aware on nVHE host. > > OK, so we definitely do need these patches, don't we? Both? Just one? > Please have a look at kvmarm/fixes and tell me what I must keep. Both of them are fixes. commit "KVM: arm64: Disable guest access to trace filter controls" - This fixes guest fiddling with the trace filter control as described above. commit "KVM: arm64: Hide system instruction access to Trace registers" - Fixes the Hypervisor to advertise what it doesn't support. i.e stop advertising trace system instruction access to a guest. Otherwise a guest which trusts the ID registers (ID_AA64DFR0_EL1.TRACEVER == 1) can crash while trying to access the trace register as we trap the accesses (CPTR_EL2.TTA == 1). On Linux, the ETM drivers need a DT explicitly advertising the support. So, this is not immediately impacted. And this fix goes a long way back in the history, when the CPTR_EL2.TTA was added. Now, the reason for asking you to hold on is the way this could create conflicts in merging the rest of the series. Suzuki