From owner-freebsd-current@freebsd.org  Thu Jan 25 22:13:22 2018
Return-Path: <owner-freebsd-current@freebsd.org>
Delivered-To: freebsd-current@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id AE748ED0FE5
 for <freebsd-current@mailman.ysv.freebsd.org>;
 Thu, 25 Jan 2018 22:13:22 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org
 [IPv6:2001:1900:2254:206a::50:5])
 by mx1.freebsd.org (Postfix) with ESMTP id 44C4C7469D
 for <freebsd-current@freebsd.org>; Thu, 25 Jan 2018 22:13:22 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: by mailman.ysv.freebsd.org (Postfix)
 id 03FD1ED0FE4; Thu, 25 Jan 2018 22:13:22 +0000 (UTC)
Delivered-To: current@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id E41EDED0FE3
 for <current@mailman.ysv.freebsd.org>; Thu, 25 Jan 2018 22:13:21 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::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 5772E7469C
 for <current@freebsd.org>; Thu, 25 Jan 2018 22:13:21 +0000 (UTC)
 (envelope-from kostikbel@gmail.com)
Received: from tom.home (kib@localhost [127.0.0.1])
 by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id w0PMDCLI008393
 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);
 Fri, 26 Jan 2018 00:13:15 +0200 (EET)
 (envelope-from kostikbel@gmail.com)
DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua w0PMDCLI008393
Received: (from kostik@localhost)
 by tom.home (8.15.2/8.15.2/Submit) id w0PMDCQJ008392;
 Fri, 26 Jan 2018 00:13:12 +0200 (EET)
 (envelope-from kostikbel@gmail.com)
X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com
 using -f
Date: Fri, 26 Jan 2018 00:13:12 +0200
From: Konstantin Belousov <kostikbel@gmail.com>
To: Ian FREISLICH <ian.freislich@capeaugusta.com>
Cc: current <current@freebsd.org>
Subject: Re: Insta-reset-bootloop with r328166 and vm.pmap.pcid_enabled=1
Message-ID: <20180125221312.GU55707@kib.kiev.ua>
References: <9e533d36-f2ee-58fc-d629-eed7d70645b4@capeaugusta.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=koi8-r
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <9e533d36-f2ee-58fc-d629-eed7d70645b4@capeaugusta.com>
User-Agent: Mutt/1.9.2 (2017-12-15)
X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00,
 DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no
 autolearn_force=no version=3.4.1
X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on tom.home
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.25
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
 <freebsd-current.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-current>, 
 <mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current/>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
 <mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 25 Jan 2018 22:13:22 -0000

On Thu, Jan 25, 2018 at 04:58:04PM -0500, Ian FREISLICH wrote:
> Hi
> 
> I cannot for the life of me recall why I had vm.pmap.pcid_enabled=1 set
> in loader.conf, but I did.š Most likely very historical reasons.
> 
> r328166 and later reset without dropping into the debugger during boot,
> no panic message.

Yes, this is how it is currently behaves.
PCID can be used to optimize PTI, see https://reviews.freebsd.org/D13985.
It is used for very differrent algorithm when PTI=1, comparing with PTI=0.