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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 5A456C433C1 for ; Wed, 24 Mar 2021 17:20:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D9C661A17 for ; Wed, 24 Mar 2021 17:20:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236700AbhCXRTx (ORCPT ); Wed, 24 Mar 2021 13:19:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:50328 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236908AbhCXRTk (ORCPT ); Wed, 24 Mar 2021 13:19:40 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E822D619FC; Wed, 24 Mar 2021 17:19:38 +0000 (UTC) Date: Wed, 24 Mar 2021 17:19:36 +0000 From: Catalin Marinas To: Suzuki K Poulose Cc: Marc Zyngier , 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 Subject: Re: [PATCH v5 05/19] arm64: Add support for trace synchronization barrier Message-ID: <20210324171934.GB3709@arm.com> 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> <59aec851-e980-0a6d-8ba5-56a35fa5a7a9@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <59aec851-e980-0a6d-8ba5-56a35fa5a7a9@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 24, 2021 at 05:06:58PM +0000, Suzuki K Poulose wrote: > 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. The way we normally work around this is to either rebase your series on top of -rc5 when the fixes go in or, if you want an earlier -rc base, Marc can put them on a stable branch somewhere that you can use. In the worst case you can merge the patches twice but that's rarely needed. -- Catalin