From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69AE6C282C2 for ; Mon, 11 Feb 2019 01:20:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B4D221736 for ; Mon, 11 Feb 2019 01:20:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726751AbfBKBUC (ORCPT ); Sun, 10 Feb 2019 20:20:02 -0500 Received: from gate.crashing.org ([63.228.1.57]:40797 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726130AbfBKBUC (ORCPT ); Sun, 10 Feb 2019 20:20:02 -0500 Received: from localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x1B0UtG5017871; Sun, 10 Feb 2019 18:30:56 -0600 Message-ID: Subject: Re: [PATCH] powerpc: fix 32-bit KVM-PR lockup and panic with MacOS guest From: Benjamin Herrenschmidt To: Mark Cave-Ayland , Christophe Leroy , paulus@samba.org, mpe@ellerman.id.au, npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org Date: Mon, 11 Feb 2019 11:30:54 +1100 In-Reply-To: <2ed8efb9-5cd4-31bf-6c7b-501b9d1925e6@ilande.co.uk> References: <20190208143319.11980-1-mark.cave-ayland@ilande.co.uk> <41b02fb0-cdc6-6de0-d8fc-44d3d0a8ad70@c-s.fr> <2ed8efb9-5cd4-31bf-6c7b-501b9d1925e6@ilande.co.uk> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.4 (3.30.4-1.fc29) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2019-02-08 at 14:51 +0000, Mark Cave-Ayland wrote: > > Indeed, but there are still some questions to be asked here: > > 1) Why were these bits removed from the original bitmask in the first place without > it being documented in the commit message? > > 2) Is this the right fix? I'm told that MacOS guests already run without this patch > on a G5 under 64-bit KVM-PR which may suggest that this is a workaround for another > bug elsewhere in the 32-bit powerpc code. > > > If you think that these points don't matter, then I'm happy to resubmit the patch > as-is based upon your comments above. We should write a test case to verify that FE0/FE1 are properly preserved/context-switched etc... I bet if we accidentally wiped them, we wouldn't notice 99.9% of the time. Cheers, Ben.