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([2600:1010:b069:668b:f917:6da4:65d8:f711]) by smtp.gmail.com with ESMTPSA id gg22sm125432pjb.20.2021.03.08.11.00.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Mar 2021 11:00:31 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v3] x86/fault: Send a SIGBUS to user process always for hwpoison page access. Date: Mon, 8 Mar 2021 11:00:28 -0800 Message-Id: <047D5B49-FDBB-494C-81E9-DA811476747D@amacapital.net> References: <4fc1b4e8f1fb4c8c81f280db09178797@intel.com> Cc: Aili Yao , Andy Lutomirski , HORIGUCHI NAOYA , Dave Hansen , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , X86 ML , yangfeng1@kingsoft.com, Linux-MM , LKML In-Reply-To: <4fc1b4e8f1fb4c8c81f280db09178797@intel.com> To: "Luck, Tony" , Oleg Nesterov , Linux API X-Mailer: iPhone Mail (18D52) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 5919040F8C30 X-Stat-Signature: aop998p6bxudohiw71gix41qkkzmrhbr Received-SPF: none (amacapital.net>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=mail-pj1-f46.google.com; client-ip=209.85.216.46 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615230032-936447 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 Mar 8, 2021, at 10:31 AM, Luck, Tony wrote: >=20 > =EF=BB=BF >>=20 >> Can you point me at that SIGBUS code in a current kernel? >=20 > It is in kill_me_maybe(). mce_vaddr is setup when we disassemble whatever= get_user() > or copy from user variant was in use in the kernel when the poison memory w= as consumed. >=20 > if (p->mce_vaddr !=3D (void __user *)-1l) { > force_sig_mceerr(BUS_MCEERR_AR, p->mce_vaddr, PAGE_SHIFT); Hmm. On the one hand, no one has complained yet. On the other hand, hardware= that supports this isn=E2=80=99t exactly common. We may need some actual ABI design here. We also need to make sure that thin= gs like io_uring accesses or, more generally, anything using the use_mm / us= e_temporary_mm ends up either sending no signal or sending a signal to the r= ight target. >=20 > Would it be any better if we used the BUS_MCEERR_AO code that goes into si= ginfo? Dunno. >=20 > That would make it match up better with what happens when poison is found > asynchronously by the patrol scrubber. I.e. the semantics are: >=20 > AR: You just touched poison at this address and need to do something about= that. > AO: Just letting you know that you have some poison at the address in sigi= nfo. >=20 > -Tony