From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (bilbo.ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3yHqhF5ZzFzDq5W for ; Fri, 20 Oct 2017 00:36:13 +1100 (AEDT) Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) by bilbo.ozlabs.org (Postfix) with ESMTP id 3yHqhF4zvNz8tBH for ; Fri, 20 Oct 2017 00:36:13 +1100 (AEDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3yHqhF1y4zz9t42 for ; Fri, 20 Oct 2017 00:36:13 +1100 (AEDT) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v9JDaB88048381 for ; Thu, 19 Oct 2017 09:36:11 -0400 Received: from e38.co.us.ibm.com (e38.co.us.ibm.com [32.97.110.159]) by mx0a-001b2d01.pphosted.com with ESMTP id 2dpu637j4t-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 19 Oct 2017 09:36:07 -0400 Received: from localhost by e38.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 19 Oct 2017 07:34:15 -0600 From: "Tulio Magno Quites Machado Filho" To: Florian Weimer , Michael Ellerman , linuxppc-dev@ozlabs.org, Adhemerval Zanella Cc: stewart@linux.vnet.ibm.com, mikey@neuling.org, cyrilbur@gmail.com Cc: Subject: Re: [PATCH 3/4] powerpc/powernv: Enable TM without suspend if possible In-Reply-To: <920a68e7-1bb5-3ace-2aaf-1594d8845721@redhat.com> References: <1507803439-12862-1-git-send-email-mpe@ellerman.id.au> <1507803439-12862-3-git-send-email-mpe@ellerman.id.au> <920a68e7-1bb5-3ace-2aaf-1594d8845721@redhat.com> Date: Thu, 19 Oct 2017 11:34:09 -0200 MIME-Version: 1.0 Content-Type: text/plain Message-Id: <8760bbb6su.fsf@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Forwarding some comments from Adhemerval sent to libc-alpha [1]... Adhemerval Zanella writes: >Florian Weimer writes: > >> On 10/12/2017 12:17 PM, Michael Ellerman wrote: >>> + pr_info("Enabling TM (Transactional Memory) with Suspend Disabled\n"); >>> + cur_cpu_spec->cpu_features |= CPU_FTR_TM; >>> + cur_cpu_spec->cpu_user_features2 |= PPC_FEATURE2_HTM_NO_SUSPEND; >>> + tm_suspend_disabled = true; >> >> This doesn't look right because if suspend is not available, you need to >> clear the original PPC_FEATURE2_HTM flag because the semantics are not >> right, so that applications can use fallback code. Otherwise, >> applications may incorrectly select the HTM code and break if running on >> a system which supports HTM, but without the suspend state. >> >> The new flag should say that HTM is supported, but without the suspend >> state, and it should be always set if PPC_FEATURE2_HTM is set. > > Will it also change TEXARS with the abort information? It should, with a permanent error cause so that old applications entering suspended state can adopt another technique. Michael, could you clarify if this is indeed happening, please? > I completely agree with Florian here, this is as *ABI* change > and the kernel need to advertise a different TM ABI instead > of as an extension. Adhemerval, could you elaborate which problems you're foreseeing, please? -- Tulio Magno [1] https://sourceware.org/ml/libc-alpha/2017-10/msg00893.html