Date: Sun, 27 Dec 2020 15:13:09 -0500 From: Andrew Gallatin <gallatin@cs.duke.edu> To: Konstantin Belousov <kib@FreeBSD.org>, src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: Re: git: d39f7430a6e1 - main - amd64: preserve %cr2 in NMI/MCE/DBG handlers. Message-ID: <f6a1732c-5365-ebec-b579-ac06f15820c6@cs.duke.edu> In-Reply-To: <202012271114.0BRBEwOO035891@gitrepo.freebsd.org> References: <202012271114.0BRBEwOO035891@gitrepo.freebsd.org>
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On 12/27/20 6:14 AM, Konstantin Belousov wrote: > The branch main has been updated by kib: > > URL: https://urldefense.com/v3/__https://cgit.FreeBSD.org/src/commit/?id=d39f7430a6e1da419d6e4fb871bca5ba7863f738__;!!OToaGQ!7EPo6uRRpq8kWDLzM05a4h158xFeRyJ9PhhE1j04Y5uZaHKskCoGhso0T717aEhpYQ$ > > commit d39f7430a6e1da419d6e4fb871bca5ba7863f738 > Author: Konstantin Belousov <kib@FreeBSD.org> > AuthorDate: 2020-12-25 21:58:43 +0000 > Commit: Konstantin Belousov <kib@FreeBSD.org> > CommitDate: 2020-12-27 10:59:33 +0000 > > amd64: preserve %cr2 in NMI/MCE/DBG handlers. > > These handlers could interrupt code which has interrupts disabled, > and if a spurious page fault occurs during exception handler run, > we get clobbered %cr2 in higher level stack. > > This is mostly a speculation, but it is based on hints from good sources. I assume this is based around the mystery panic I was talking about on irc last week. Can you please explain what a spurious page fault is? A fault where there is a valid mapping, but we somehow take a fault for no reason? How often does this happen? Drew
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