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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 0E482C2D0CF for ; Tue, 24 Dec 2019 10:29:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE24A20409 for ; Tue, 24 Dec 2019 10:29:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726283AbfLXK3x (ORCPT ); Tue, 24 Dec 2019 05:29:53 -0500 Received: from foss.arm.com ([217.140.110.172]:50936 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726104AbfLXK3x (ORCPT ); Tue, 24 Dec 2019 05:29:53 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 93FCF31B; Tue, 24 Dec 2019 02:29:52 -0800 (PST) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0C4773F6CF; Tue, 24 Dec 2019 02:29:51 -0800 (PST) Date: Tue, 24 Dec 2019 10:29:50 +0000 From: Andrew Murray To: Marc Zyngier Cc: will@kernel.org, Catalin Marinas , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sudeep Holla , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 02/18] arm64: KVM: reset E2PB correctly in MDCR_EL2 when exiting the guest(VHE) Message-ID: <20191224102949.GD42593@e119886-lin.cambridge.arm.com> References: <20191220143025.33853-1-andrew.murray@arm.com> <20191220143025.33853-3-andrew.murray@arm.com> <20191221131214.769a140e@why> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191221131214.769a140e@why> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 21, 2019 at 01:12:14PM +0000, Marc Zyngier wrote: > On Fri, 20 Dec 2019 14:30:09 +0000 > Andrew Murray wrote: > > > From: Sudeep Holla > > > > On VHE systems, the reset value for MDCR_EL2.E2PB=b00 which defaults > > to profiling buffer using the EL2 stage 1 translations. > > Does the reset value actually matter here? I don't see it being > specific to VHE systems, and all we're trying to achieve is to restore > the SPE configuration to a state where it can be used by the host. > > > However if the > > guest are allowed to use profiling buffers changing E2PB settings, we > > How can the guest be allowed to change E2PB settings? Or do you mean > here that allowing the guest to use SPE will mandate changes of the > E2PB settings, and that we'd better restore the hypervisor state once > we exit? > > > need to ensure we resume back MDCR_EL2.E2PB=b00. Currently we just > > do bitwise '&' with MDCR_EL2_E2PB_MASK which will retain the value. > > > > So fix it by clearing all the bits in E2PB. > > > > Signed-off-by: Sudeep Holla > > Signed-off-by: Andrew Murray > > --- > > arch/arm64/kvm/hyp/switch.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c > > index 72fbbd86eb5e..250f13910882 100644 > > --- a/arch/arm64/kvm/hyp/switch.c > > +++ b/arch/arm64/kvm/hyp/switch.c > > @@ -228,9 +228,7 @@ void deactivate_traps_vhe_put(void) > > { > > u64 mdcr_el2 = read_sysreg(mdcr_el2); > > > > - mdcr_el2 &= MDCR_EL2_HPMN_MASK | > > - MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT | > > - MDCR_EL2_TPMS; > > + mdcr_el2 &= MDCR_EL2_HPMN_MASK | MDCR_EL2_TPMS; > > > > write_sysreg(mdcr_el2, mdcr_el2); > > > > I'm OK with this change, but I believe the commit message could use > some tidying up. No problem, I'll update the commit message. Thanks, Andrew Murray > > Thanks, > > M. > -- > Jazz is not dead. It just smells funny...