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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 E7F27C433EF for ; Mon, 20 Sep 2021 13:40:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE14760F93 for ; Mon, 20 Sep 2021 13:40:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239451AbhITNmK (ORCPT ); Mon, 20 Sep 2021 09:42:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:50376 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239325AbhITNmJ (ORCPT ); Mon, 20 Sep 2021 09:42:09 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 32B9260F21; Mon, 20 Sep 2021 13:40:42 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mSJXE-00Bm01-5z; Mon, 20 Sep 2021 14:40:40 +0100 Date: Mon, 20 Sep 2021 14:40:39 +0100 Message-ID: <87o88nuzzc.wl-maz@kernel.org> From: Marc Zyngier To: Paolo Bonzini Cc: Peter Zijlstra , Sean Christopherson , Ingo Molnar , Arnaldo Carvalho de Melo , Will Deacon , Mark Rutland , Catalin Marinas , Guo Ren , Nick Hu , Greentime Hu , Vincent Chen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Borislav Petkov , x86@kernel.org, Boris Ostrovsky , Juergen Gross , Alexander Shishkin , Jiri Olsa , Namhyung Kim , James Morse , Alexandru Elisei , Suzuki K Poulose , "H. Peter Anvin" , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Stefano Stabellini , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-csky@vger.kernel.org, linux-riscv@lists.infradead.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, Artem Kashkanov , Like Xu , Zhu Lingshan Subject: Re: [PATCH v2 00/13] perf: KVM: Fix, optimize, and clean up callbacks In-Reply-To: <7a5825d1-d6e9-8ac8-5df2-cce693525da7@redhat.com> References: <20210828003558.713983-1-seanjc@google.com> <20210828201336.GD4353@worktop.programming.kicks-ass.net> <662e93f9-e858-689d-d203-742731ecad2c@redhat.com> <87tuifv3mb.wl-maz@kernel.org> <7a5825d1-d6e9-8ac8-5df2-cce693525da7@redhat.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: pbonzini@redhat.com, peterz@infradead.org, seanjc@google.com, mingo@redhat.com, acme@kernel.org, will@kernel.org, mark.rutland@arm.com, catalin.marinas@arm.com, guoren@kernel.org, nickhu@andestech.com, green.hu@gmail.com, deanbo422@gmail.com, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, tglx@linutronix.de, bp@alien8.de, x86@kernel.org, boris.ostrovsky@oracle.com, jgross@suse.com, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, hpa@zytor.com, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, sstabellini@kernel.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-csky@vger.kernel.org, linux-riscv@lists.infradead.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, artem.kashkanov@intel.com, like.xu.linux@gmail.com, lingsha n.zhu@intel.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, 20 Sep 2021 14:18:30 +0100, Paolo Bonzini wrote: > > On 20/09/21 14:22, Marc Zyngier wrote: > >> I think that's only ARM, and even then it is only because of > >> limitations of the hardware which mostly apply only if VHE is not in > >> use. > >> > >> If anything, it's ARM that should support module build in VHE mode > >> (Linux would still need to know whether it will be running at EL1 or > >> EL2, but KVM's functionality is as self-contained as on x86 in the VHE > >> case). > > I don't see this happening anytime soon. At least not before we > > declare the arm64 single kernel image policy to be obsolete. > > --verbose please. :) I am sure you're right, but I don't understand > the link between the two. To start making KVM/arm64 modular, you'd have to build it such as there is no support for the nVHE hypervisor anymore. Which would mean two different configs (one that can only work with VHE, and one for the rest) and contradicts the current single kernel image policy. It is bad enough that we have to support 3 sets of page sizes. Doubling the validation space for the sake of being able to unload KVM seems a dubious prospect. M. -- Without deviation from the norm, progress is not possible.