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 A3E29C433EF for ; Tue, 15 Feb 2022 18:57:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243311AbiBOS6E (ORCPT ); Tue, 15 Feb 2022 13:58:04 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:41628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243309AbiBOS6D (ORCPT ); Tue, 15 Feb 2022 13:58:03 -0500 Received: from mail-io1-xd31.google.com (mail-io1-xd31.google.com [IPv6:2607:f8b0:4864:20::d31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 291FAB150C for ; Tue, 15 Feb 2022 10:57:53 -0800 (PST) Received: by mail-io1-xd31.google.com with SMTP id r144so25050387iod.9 for ; Tue, 15 Feb 2022 10:57:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=xYfVux+CIlABTBnGP+1TuKUKEth7AQ/+EngXOD7SJRc=; b=c0Itl5iwd/n5gn0l5gRQjED/Gm+0SUMu0QvAZlzu6Uunay0OCCnebIYN2QLWE/vgr0 b1SRkggvbPIBirN3uR9G5/FqbZZKRlx3HIl6zHi42iNs9pE++n4yCWMnWxJsWqTcwU97 y2RWZMGWmQAMWgWTGZH6Hw6PF/jimIW8xqlfEhLrp3ruxE/g8+tVDBosnyy5nZH+16bF RyFh4PQA5cMTq7MPRu9GGizYCvIm5yOLfVSYyjfCM01wVqZged3cV+8o2n2goyKDU05h E2Rf2bZhDgmsgls83iQbHlO7n8aKBGV3ARfKHLKQIIYuZ5+qtEwnDjS8agz5x+/My3w8 OQfA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=xYfVux+CIlABTBnGP+1TuKUKEth7AQ/+EngXOD7SJRc=; b=4jKjOqzIZuwXXVYxVRkY9N1Pyda9Bsn89igMw7/qqdbH0clac9Etcmvuvkrn/nEqdS rC90kliBibAg2U90j8ta/te/2rxprTFAMJEQi4MU7hUaaj8C4WIFhfPCUEqMyy60U/Td u6st9CN1VYFUTXDKzYo9j8m92O0se50tuqV8X8sIYQMP3w+ALGr9z3n10nr92E/rp02E 5g9UVYxizYUoQf5pAOPwf7i9vvxzN96XCIu4VrDG7+036u6osjry0ehV8bctfcdUT47W Az2bXC1l8qiWMLxXihFajbWuBLEpPcvmSxiEQsjUkSYs2haS1MSAVB5nnXD5Z86J20WG NTtw== X-Gm-Message-State: AOAM530oZBNb+s4aaX9IlMMAPbrnRsKRiVA9SpkzMHY5fv2TDyWvhPq6 DYnygkFvPQVZX3F+EYjblWVa+w== X-Google-Smtp-Source: ABdhPJwBqvknVuwUJVoIKC4yoStt6Wy8q4gp/ncMH7iNUF6wTE+Enpcr3H0D3NZSs3azu2iT2aFs3Q== X-Received: by 2002:a02:c90a:: with SMTP id t10mr220027jao.142.1644951472295; Tue, 15 Feb 2022 10:57:52 -0800 (PST) Received: from google.com (194.225.68.34.bc.googleusercontent.com. [34.68.225.194]) by smtp.gmail.com with ESMTPSA id t195sm16834393iof.47.2022.02.15.10.57.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Feb 2022 10:57:51 -0800 (PST) Date: Tue, 15 Feb 2022 18:57:47 +0000 From: Oliver Upton To: Reiji Watanabe Cc: Marc Zyngier , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, James Morse , Alexandru Elisei , Suzuki K Poulose , Paolo Bonzini , Will Deacon , Andrew Jones , Fuad Tabba , Peng Liang , Peter Shier , Ricardo Koller , Jing Zhang , Raghavendra Rao Anata Subject: Re: [PATCH v5 10/27] KVM: arm64: Hide IMPLEMENTATION DEFINED PMU support for the guest Message-ID: References: <20220214065746.1230608-1-reijiw@google.com> <20220214065746.1230608-11-reijiw@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220214065746.1230608-11-reijiw@google.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Reiji, On Sun, Feb 13, 2022 at 10:57:29PM -0800, Reiji Watanabe wrote: > When ID_AA64DFR0_EL1.PMUVER or ID_DFR0_EL1.PERFMON is 0xf, which > means IMPLEMENTATION DEFINED PMU supported, KVM unconditionally > expose the value for the guest as it is. Since KVM doesn't support > IMPLEMENTATION DEFINED PMU for the guest, in that case KVM should > expose 0x0 (PMU is not implemented) instead. > > Change cpuid_feature_cap_perfmon_field() to update the field value > to 0x0 when it is 0xf. Definitely agree with the change in this patch. Do we need to tolerate writes of 0xf for ABI compatibility (even if it is nonsensical)? Otherwise a guest with IMP_DEF PMU cannot be migrated to a newer kernel. -- Thanks, Oliver