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Mon, 20 Jul 2020 04:31:02 +0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 06K4Ux6a33620128 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 20 Jul 2020 04:31:00 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E17CFAE055; Mon, 20 Jul 2020 04:30:59 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 72E48AE045; Mon, 20 Jul 2020 04:30:57 +0000 (GMT) Received: from [9.199.36.102] (unknown [9.199.36.102]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 20 Jul 2020 04:30:57 +0000 (GMT) Subject: Re: [PATCH v2 2/3] powerpc/powernv/idle: save-restore DAWR0, DAWRX0 for P10 To: Nicholas Piggin , Pratik Rajesh Sampat References: <20200710052207.12003-1-psampat@linux.ibm.com> <20200710052207.12003-3-psampat@linux.ibm.com> <1594619458.45vrahx59w.astroid@bobo.none> From: Ravi Bangoria Message-ID: Date: Mon, 20 Jul 2020 10:00:56 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1594619458.45vrahx59w.astroid@bobo.none> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-07-19_04:2020-07-17, 2020-07-19 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 malwarescore=0 mlxscore=0 adultscore=0 suspectscore=0 bulkscore=0 phishscore=0 mlxlogscore=834 spamscore=0 impostorscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007200025 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: , Cc: ego@linux.vnet.ibm.com, mikey@neuling.org, pratik.r.sampat@gmail.com, linux-kernel@vger.kernel.org, paulus@samba.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Nick, On 7/13/20 11:22 AM, Nicholas Piggin wrote: > Excerpts from Pratik Rajesh Sampat's message of July 10, 2020 3:22 pm: >> Additional registers DAWR0, DAWRX0 may be lost on Power 10 for >> stop levels < 4. >> Therefore save the values of these SPRs before entering a "stop" >> state and restore their values on wakeup. > > Hmm, where do you get this from? Documentation I see says DAWR is lost > on POWER9 but not P10. > > Does idle thread even need to save DAWR, or does it get switched when > going to a thread that has a watchpoint set? I don't know how idle states works internally but IIUC, we need to save/restore DAWRs. This is needed when user creates per-cpu watchpoint event. Ravi