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Tue, 09 Apr 2024 15:41:19 -0700 (PDT) Received: from smtpclient.apple ([103.98.78.154]) by smtp.gmail.com with ESMTPSA id g26-20020aa79f1a000000b006ecee8c8c0fsm7200440pfr.176.2024.04.09.15.41.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Apr 2024 15:41:18 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Joel Fernandes Mime-Version: 1.0 (1.0) Subject: Re: [POC][RFC][PATCH 0/2] pstore/mm/x86: Add wildcard memmap to map pstore consistently Date: Wed, 10 Apr 2024 04:11:05 +0530 Message-Id: <9F1B6537-F0BF-46E1-92A2-92C082DDB573@joelfernandes.org> References: Cc: Kees Cook , Steven Rostedt , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , "Guilherme G. Piccoli" , linux-hardening@vger.kernel.org, Guenter Roeck , Ross Zwisler , wklin@google.com, Vineeth Remanan Pillai , Suleiman Souhlal , Linus Torvalds , Catalin Marinas , Will Deacon In-Reply-To: To: "Luck, Tony" X-Mailer: iPhone Mail (21D61) X-Stat-Signature: ixg6tschirrfh8wnz9beuia8z4pdu5tn X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9207E100007 X-Rspam-User: X-HE-Tag: 1712702480-290528 X-HE-Meta: U2FsdGVkX19xknnbSE2Fx5MWpy11nh2Qw/O/8PDaWyFR4k1j+Iwn4WtJFKYqpQZ3AO/sACxGX9FNvYhGNfuTB8GnsToPQJ40jVcuV8iaepoiCeezIRsDNhf4+qf+bWbya2jSvZzLs8ounac2WQnPOG4qgVru+dhSAth3HiI6likQHU39Erhu1p0pgL0J9mFI+wDpJORnbqc53H/ZWP+KC2tyJxjmrT6/EbwYLUqHD5SU2A4+pgmsEpWah0SIqE0a9abim9aNfOhgBe6ZoRqeM07HvLTd7kHf0+Q1OGs024s24z/L0nh51khDLdTQKCao+yjUyZxxGkCWbWOo4Cenl/JGqRMerLocoVxv3SsogSNsVZU/0KeKqL7eDngau2eVS4RM60bxqq7D2/1CKiWgBXnXLFDrZ3fSMnP4qo5/bC9Mf7RPh5j3j1Eddm2A58UkoKrH2D7wMztqIRRaigECoeBq9wooMlb0uWp9/BfAonsmR6RqwRC3WW5ZcpbSZUEioHxNL1SurQ7FpbpQqfTt5Q5oCkv1TQRIDwlY7W1VQ03lBAr5JWVhgziHTqdvh1gnX56cQGeoJGGJgIvPD24hW8v4M3M8DRZdIQYiIqhCVT22T1egpq1+3ml32LBsVloAWLsNRcVYwcGr+m3IRfpNAvj7BqMNk3Ao5o9OluEcE4UL7bOuvMbqQ3kGslyRzFNt1G42TgPrHMQyOkiGHeJJgpC8K12sB/oXqHOMCRV5ljQhPAM6YERggkCNwaWV3BrBnHOrODIDyREUs03YppUOQIbtSfdOZJDZ1qY9frgnz5xK7oeNSaBCtgkK+1L9an6okA7OYSf8ePxYqR8MKHvAnisTlG8MuhTB7heZakl5xUQAeKU44RMiQ+2Gg+mzX01jraJVGnHLIudKJ7P9w3wIH3p1Bv2ZZhoipAb2sBSri1d25TFCp2MkqlMhory+3opg4iQX5Fu+tmUpckDBQjg 8OEbQmUD Tgo39jGaD/n/RupehLyXB2T5Q0XjxvgPrkDFGYDk9OE2JoiQXJD4U78A2fCyCWN4DEptyn67R73/wBCb1eXXrZMBMqdJG28mqJBTCYFR8JC5sUTUWpgivdqH58UT3W1eqmXXvPl7X84zZZhehbz4dqYho9bvw19y8Hv6c27OCvb2W1AsegmhFTDGRwabK5AziXKwUKnIB518m1xOS/wGrf/CFOQ14g3OBk6kp8NtnvovHf3eISCR79XPiXtxhZoRGax48wNqoQRjvJd+4BVF6gN/hyzClQT8gNknEGRR9aYmOFe33LiHlAgZtZm0y+tIcfS0BpDF+WTptzWhHp6QpOkPZwAB+SSgPQWCS5kMI1EyK3+0ldoPjVFIaDuhEiH+5PckGdcAPUiSZVKTe74zDCglEdw== 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: List-Subscribe: List-Unsubscribe: > On Apr 10, 2024, at 3:55=E2=80=AFAM, Luck, Tony wrot= e: >=20 > =EF=BB=BF >>=20 >>> I forgot to mention that this makes it trivial for any machine that does= n't >>> clear memory on soft-reboot, to enable console ramoops (to have access t= o >>> the last boot dmesg without needing serial). >>>=20 >>> I tested this on a couple of my test boxes and on QEMU, and it works rat= her >>> well. >>=20 >> I've long wanted a "stable for this machine and kernel" memory region >> like this for pstore. It would make testing much easier. >=20 > Which systems does this work on? I'd assume that servers (and anything > else with ECC memory) would nuke contents while resetting ECC to clean > state. If that were the case universally, then ramoops pstore backend would not wor= k either? And yet we get the last kernel logs via the pstore for many years now, on em= bedded-ish devices. =46rom my reading, ECC-enabled DRAM is not present on lots of systems and II= RC, pstore ramoops has its own ECC. Or did I miss a recent trend with ECC-enabled DRAM? - Joel >=20 > -Tony