From owner-freebsd-ppc@freebsd.org Sat Apr 1 18:53:18 2017 Return-Path: Delivered-To: freebsd-ppc@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 47156D299EE for ; Sat, 1 Apr 2017 18:53:18 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (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 35F1D6C9 for ; Sat, 1 Apr 2017 18:53:18 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id v31IrHIx028691 for ; Sat, 1 Apr 2017 18:53:18 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-ppc@FreeBSD.org Subject: [Bug 205458] 11.0-CURRENT/10-STABLE powerpc64: a PowerMac G5 specific sys/powerpc/ofw/ofw_machdep.c change for reliable PowerMac G5 booting (with lots of RAM) Date: Sat, 01 Apr 2017 18:53:17 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: patch X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: commit-hook@freebsd.org X-Bugzilla-Status: In Progress X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: jhibbits@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-ppc@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Porting FreeBSD to the PowerPC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 01 Apr 2017 18:53:18 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D205458 --- Comment #18 from commit-hook@freebsd.org --- A commit references this bug: Author: jhibbits Date: Sat Apr 1 18:52:49 UTC 2017 New revision: 316367 URL: https://svnweb.freebsd.org/changeset/base/316367 Log: MFC r314885: Fix booting with >4GB RAM on PowerMac G5 hardware =3D=3D=3D From Nathan Whitehorn: Open Firmware runs in virtual mode on the Powermac G5. This runs inside the kernel page table, which preserves all address translations made by OF before the kernel starts; as a result, the kernel address space is a strict superset of OF's. Where this explodes is if OF uses an unmapped SLB entry. The SLB fault handler runs in real mode and refers to the PCPU pointer in SPRG0, which blows up the kernel. Having a value of SPRG0 that works for the kernel is less fatal than preserving OF's value in this case. =3D=3D=3D The result of this is seemingly random panics from NULL dereferences, or hangs immediately upon boot. By not restoring SPRG0 for Open Firmware entry the kernel PCPU pointer is preserved and SLB faults are successful, resulting in a stable kernel. PR: 205458 Changes: _U stable/11/ stable/11/sys/powerpc/ofw/ofw_machdep.c --=20 You are receiving this mail because: You are on the CC list for the bug.=