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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 6 Mar 2020 04:45:44 -0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0264iifv49021392 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 6 Mar 2020 04:44:44 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0AFF842045; Fri, 6 Mar 2020 04:45:43 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AAD3A42041; Fri, 6 Mar 2020 04:45:42 +0000 (GMT) Received: from ozlabs.au.ibm.com (unknown [9.192.253.14]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 6 Mar 2020 04:45:42 +0000 (GMT) Received: from [10.61.2.125] (haven.au.ibm.com [9.192.254.114]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by ozlabs.au.ibm.com (Postfix) with ESMTPSA id B080AA011F; Fri, 6 Mar 2020 15:45:37 +1100 (AEDT) Subject: Re: [PATCH v2] powerpc: setup_64: set up PACA earlier to avoid kcov problems To: Daniel Axtens , linuxppc-dev@lists.ozlabs.org References: <20200213052327.24207-1-dja@axtens.net> <59e8a506-572a-f355-e0ca-9c75758a9b65@linux.ibm.com> <87zhcup02u.fsf@dja-thinkpad.axtens.net> From: Andrew Donnellan Date: Fri, 6 Mar 2020 15:45:41 +1100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <87zhcup02u.fsf@dja-thinkpad.axtens.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20030604-0020-0000-0000-000003B0F552 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20030604-0021-0000-0000-00002209340B Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-03-05_08:2020-03-05, 2020-03-05 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxlogscore=999 suspectscore=0 impostorscore=0 priorityscore=1501 bulkscore=0 phishscore=0 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003060031 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 6/3/20 3:40 pm, Daniel Axtens wrote: >> There's some special handling for CPU_FTR_HVMODE in >> cpufeatures_setup_cpu() in kernel/dt_cpu_ftrs.c: >> >> /* Initialize the base environment -- clear FSCR/HFSCR. */ >> hv_mode = !!(mfmsr() & MSR_HV); >> if (hv_mode) { >> /* CPU_FTR_HVMODE is used early in PACA setup */ >> cur_cpu_spec->cpu_features |= CPU_FTR_HVMODE; >> mtspr(SPRN_HFSCR, 0); >> } >> >> With this patch, the comment about PACA setup I assume is no longer >> true. It looks like we still rely on hv_mode being set to deal with >> discrepancies between the device tree and the MSR. > > This code confuses me. IIUC it sets the CPU feature if we're in HV mode, > which will catch the case where the HV bit is set in the MSR but for > some reason it's not listed in the DT. With my patch, we'll directly > test the MSR so we don't need the cpu feature set for that. > > However, the CPU feature is tested elsewhere, so I think the correct > behaviour is to keep the code but drop the comment. Having said that > bootstrapping is hard so lmk if I've misunderstood. That was my thinking too. -- Andrew Donnellan OzLabs, ADL Canberra ajd@linux.ibm.com IBM Australia Limited