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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 26 Mar 2019 13:54:25 -0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x2QDsOpU47841348 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Mar 2019 13:54:24 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 18E654C046; Tue, 26 Mar 2019 13:54:24 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2A4894C040; Tue, 26 Mar 2019 13:54:23 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.207.52]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 26 Mar 2019 13:54:23 +0000 (GMT) Date: Tue, 26 Mar 2019 15:54:21 +0200 From: Mike Rapoport To: Anshuman Khandual Cc: "linux-mm@kvack.org" , Andrew Morton , Michal Hocko , Dave Hansen , Vladimir Murzin , Tony Luck , Dan Williams Subject: Re: early_memtest() patterns References: <7da922fb-5254-0d3c-ce2b-13248e37db83@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7da922fb-5254-0d3c-ce2b-13248e37db83@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19032613-0012-0000-0000-0000030750B4 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19032613-0013-0000-0000-0000213E796B Message-Id: <20190326135420.GA23024@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-26_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=478 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903260098 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 26, 2019 at 01:39:14PM +0530, Anshuman Khandual wrote: > Hello, > > early_memtest() is being executed on many platforms even though they dont enable > CONFIG_MEMTEST by default. Just being curious how the following set of patterns > got decided. Are they just random 64 bit patterns ? Or there is some particular > significance to them in detecting bad memory. > > static u64 patterns[] __initdata = { > /* The first entry has to be 0 to leave memtest with zeroed memory */ > 0, > 0xffffffffffffffffULL, > 0x5555555555555555ULL, > 0xaaaaaaaaaaaaaaaaULL, > 0x1111111111111111ULL, > 0x2222222222222222ULL, > 0x4444444444444444ULL, > 0x8888888888888888ULL, > 0x3333333333333333ULL, > 0x6666666666666666ULL, > 0x9999999999999999ULL, > 0xccccccccccccccccULL, > 0x7777777777777777ULL, > 0xbbbbbbbbbbbbbbbbULL, > 0xddddddddddddddddULL, > 0xeeeeeeeeeeeeeeeeULL, > 0x7a6c7258554e494cULL, /* yeah ;-) */ > }; > > BTW what about the last one here. It's 'LINUXrlz' ;-) > - Anshuman > -- Sincerely yours, Mike.