From owner-dev-commits-src-main@freebsd.org Sun Dec 27 20:13:12 2020 Return-Path: Delivered-To: dev-commits-src-main@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id DED984C52F5; Sun, 27 Dec 2020 20:13:12 +0000 (UTC) (envelope-from gallatin@cs.duke.edu) Received: from duke.cs.duke.edu (duke.cs.duke.edu [152.3.140.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4D3sLc5mv5z3Lwp; Sun, 27 Dec 2020 20:13:12 +0000 (UTC) (envelope-from gallatin@cs.duke.edu) Received: from [192.168.0.75] (d-137-103-47-117.fl.cpe.atlanticbb.net [137.103.47.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: gallatin) by duke.cs.duke.edu (Postfix) with ESMTPSA id 65B002700178; Sun, 27 Dec 2020 15:13:11 -0500 (EST) DMARC-Filter: OpenDMARC Filter v1.3.1 duke.cs.duke.edu 65B002700178 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=cs.duke.edu; s=mail0816; t=1609099991; bh=CMIt8ymdRUmtDIAuARdXgnIHVW9ItTlJ7wwtET+GSr0=; h=Subject:To:From:Date:From; b=K4/6jlSvWQ5h2DZEXGDxtR1gMzB3dq6h30P6xgp3IeeuC37G8ABg7Sno74TKXtvpF ySZTpALcwNAyaaOTiAMQ9usCLzz9SDoRjRbFcma9VVXniYEKnJqb7qBddBOee4B1kn MLiYmzEocQMYgnwP7GmxlIN49699kr+DHbcnoPyAxvdTyDkYC+9G4lBsEcQ8PlZepY qLRy44YiQHQamPPP7hlYo+t0nN5JJ36D0mSpbqBeXPGyE0s364BJcgiSK6A23q7Sn6 tHj3u33iJg9SaJO1TYkvG8hrhNf0PJNEgvnN7PNDWZOeGPU/sfUzc14pDI26LeNk1f TYVzeKqb5qigw== Subject: Re: git: d39f7430a6e1 - main - amd64: preserve %cr2 in NMI/MCE/DBG handlers. To: Konstantin Belousov , src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org References: <202012271114.0BRBEwOO035891@gitrepo.freebsd.org> From: Andrew Gallatin Message-ID: Date: Sun, 27 Dec 2020 15:13:09 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <202012271114.0BRBEwOO035891@gitrepo.freebsd.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4D3sLc5mv5z3Lwp X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-BeenThere: dev-commits-src-main@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: "Commit messages for the main branch of the src repository." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 27 Dec 2020 20:13:12 -0000 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 > AuthorDate: 2020-12-25 21:58:43 +0000 > Commit: Konstantin Belousov > 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