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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DAA65C32771 for ; Wed, 28 Sep 2022 16:12:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234372AbiI1QMl (ORCPT ); Wed, 28 Sep 2022 12:12:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233190AbiI1QMj (ORCPT ); Wed, 28 Sep 2022 12:12:39 -0400 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E1C2C6DF93 for ; Wed, 28 Sep 2022 09:12:38 -0700 (PDT) Received: by mail-pj1-x1034.google.com with SMTP id q15-20020a17090a304f00b002002ac83485so2137815pjl.0 for ; Wed, 28 Sep 2022 09:12:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date; bh=SX46qqsXP6rNXBfhWbDF1CWQd9NesON2YiNX3aiOXY0=; b=fzDC1W22cfZ4eDT1CC0OBYGcpwDVGaIUNn9gpp+5Om3tsWLsgyETbIAFuKLDILPNOF NEEiTgMTRAUHTfaXUgf3Yr6pWUc0h8FDYlycrjTCqUs2iP6brpgSe2PUc3K/KC2zDHyN y+EjT27JXL79rXS7ZeoidlEdf3yPQlonDfwh1D5RMd/M4SKBv3uFQK7SpAzozqBJjMJT bSbDSUNDFa9pQlgJxRwPcRQJIIG1LlttRThlG3BNyEouNJCP0aREDQsErYXBSFSkfBrA FCT42XP9Mrup9YwTWBjCl/U7F5pEbpKrIXeGIuwX/lIkG+uDAe+1SRLTOjqh490JtHor Gu/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=SX46qqsXP6rNXBfhWbDF1CWQd9NesON2YiNX3aiOXY0=; b=i0KH9fxTtTQ5HMRi1MtTMJoSJPhAp0gpdJ3he5hBfKLAHJzJspo/ydXnth9x0WMWMv /ZIIC7o9x+rF8oS7wDJ8jqHFHnrQy8nq30NYTy0MeBjYWgzqiaBZBm/l51WRdBZOweqj iB3eAiJwiF17TrgDXWi7U4PMuSR6QkKNwrkABJK4tNxn34SbNpqD5WwL1S/gA100cOQ0 PumPOJWOk8QlJZvh/WOK8FEmW/XCRcY5bE7MGEn6ba7Ag+EYY4w9QKQnrKBAeOgavVLP vS0BtGphUs04z4JIVwYYkAiEcQZeKidcXpsXbTwoAYVmueu4FM8nnh54kHEDArqGqY4Y whBQ== X-Gm-Message-State: ACrzQf18tdUy1AYnPl8Ou4sv4smWX7Jt4QfpzwFRrg27O48n4LVylSsa QW524/e/AESz8EyTy7sJJN7jfg== X-Google-Smtp-Source: AMsMyM4CQonqEyArDPEJ70zxw16cAnQiwAeyZhblK/Tv64BVxU1faRMq7OaiZPq+tjiBxsdTcgQMaw== X-Received: by 2002:a17:903:2305:b0:178:380f:5246 with SMTP id d5-20020a170903230500b00178380f5246mr554123plh.146.1664381558359; Wed, 28 Sep 2022 09:12:38 -0700 (PDT) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id d128-20020a623686000000b0053e66f57334sm4194923pfa.112.2022.09.28.09.12.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Sep 2022 09:12:37 -0700 (PDT) Date: Wed, 28 Sep 2022 16:12:33 +0000 From: Sean Christopherson To: Paolo Bonzini Cc: Maxim Levitsky , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH] KVM: x86: disable on 32-bit unless CONFIG_BROKEN Message-ID: References: <20220926165112.603078-1-pbonzini@redhat.com> <15291c3f-d55c-a206-9261-253a1a33dce1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <15291c3f-d55c-a206-9261-253a1a33dce1@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Sep 28, 2022, Paolo Bonzini wrote: > On 9/28/22 09:10, Maxim Levitsky wrote: > > I also think that outside KVM developers nobody should be using KVM on 32 bit host. > > > > However for_developement_ I think that 32 bit KVM support is very useful, as it > > allows to smoke test the support for 32 bit nested hypervisors, which I do once in a while, > > and can even probably be useful to some users (e.g running some legacy stuff in a VM, > > which includes a hypervisor, especially to run really legacy OSes / custom bare metal software, > > using an old hypervisor) - or in other words, 32 bit nested KVM is mostly useless, but > > other 32 bit nested hypervisors can be useful. > > > > Yes, I can always use an older 32 bit kernel in a guest with KVM support, but as long > > as current kernel works, it is useful to use the same kernel on host and guest. > > Yeah, I would use older 32 bit kernels just like I use RHEL4 to test PIT > reinjection. :) But really the ultimate solution to this would be to > improve kvm-unit-tests so that we can compile vmx.c and svm.c for 32-bit. Agreed. I too use 32-bit KVM to validate KVM's handling of 32-bit L1 hypervisors, but the maintenance cost is painfully high.