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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 CA5FBC433ED for ; Fri, 30 Apr 2021 19:43:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9ABA461151 for ; Fri, 30 Apr 2021 19:43:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232265AbhD3Tnz (ORCPT ); Fri, 30 Apr 2021 15:43:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230508AbhD3Tnw (ORCPT ); Fri, 30 Apr 2021 15:43:52 -0400 Received: from mail-pg1-x529.google.com (mail-pg1-x529.google.com [IPv6:2607:f8b0:4864:20::529]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56C6CC06174A for ; Fri, 30 Apr 2021 12:43:03 -0700 (PDT) Received: by mail-pg1-x529.google.com with SMTP id j189so3093191pgd.13 for ; Fri, 30 Apr 2021 12:43:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sTsNm6Ls4TUy5ckEe/aB3j0eDGPr1MXObQaGCGMAocE=; b=lN9muvcXbwSPl+TaH5GLQ8oX4P5CO9Mgkx/U/wX+rBit/3d0X0MZXNioHL1hv7ig3W WBUnkBSV5C8yd1doS7DQBWx+4W3zAoELx7I1SgLraW/Zqk7jMmbbA5ETtEUoC6a+pv/o itLUPlp46SU3JbUv3swZNM2/ULMZb9+ncnlakg+yAvPRj1NCRWfFOE3L66tVd0SBx2/e pxuKAtRJ1pY1LaG3/w+HbdP2AOcyUU9Ex6wGi/OOxhSfmzAldG1DXecnRZnu/UHPhwhg N5i4ZIBhGGNMRfB0LVwQeMY6tM6JpLjzy/NjEs8kMABtO/h1XzUTFTgDR1MW/wo47Ytf 5rWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sTsNm6Ls4TUy5ckEe/aB3j0eDGPr1MXObQaGCGMAocE=; b=LXCMAwRtki3rkKe2WPLOmBc8q68vB7xHFeAL6eSVl2e2rANKKWoC4LWcJtOXka6tsY 2+5+z3KnTLG37wuQKzBonHhcouyOuEKvJYAYyN14OuPipdys3ehmdXM5/y8ELsEOKu5e kW/IzVWMv4Awz6iCPHroR6CVE6gYjX85Xjy+mQDCYerOm/no8spIr2MOBiAGr3p0wIf6 SFHuAEoG6YU+eSdVQTheLQC+0/M65u0YHlutUsTvtKE6zik/lxcd7OeYF3is5SxxG7Qm nPndpPtF0dxfUNtAlRK2VNEoGQo+mhZBlHFafxYiREhqqyNEdEuVt8LznsUyJGeUXpVa 5+0g== X-Gm-Message-State: AOAM5307ETrrJKF55xdMKuj7k+WmcIjPaE8QTHzhZK9gyYSnK3t44POd JrZG16rncStT8PvyG6xdKM7EUgDP/RD2enlP0J9E7V/kvJVipIri X-Google-Smtp-Source: ABdhPJxNM+CocJtBk1fxCsWHqK0IQip/tJ5KmZIYqj3Nd01BifyBBkKw4peHw8Y37id6AI0Ic/qE4abGfr4hTQXoALc= X-Received: by 2002:aa7:91d1:0:b029:1fe:2a02:73b9 with SMTP id z17-20020aa791d10000b02901fe2a0273b9mr6637574pfa.2.1619811782689; Fri, 30 Apr 2021 12:43:02 -0700 (PDT) MIME-Version: 1.0 References: <20210430131733.192414-1-rsaripal@amd.com> <20210430131733.192414-2-rsaripal@amd.com> In-Reply-To: <20210430131733.192414-2-rsaripal@amd.com> From: Reiji Watanabe Date: Fri, 30 Apr 2021 12:42:46 -0700 Message-ID: Subject: Re: [PATCH v4 1/1] x86/cpufeatures: Implement Predictive Store Forwarding control. To: Ramakrishna Saripalli Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, Jonathan Corbet , bsd@redhat.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > +static int __init psf_cmdline(char *str) > +{ > + u64 tmp = 0; > + > + if (!boot_cpu_has(X86_FEATURE_PSFD)) > + return 0; > + > + if (!str) > + return -EINVAL; > + > + if (!strcmp(str, "off")) { > + set_cpu_cap(&boot_cpu_data, X86_FEATURE_MSR_SPEC_CTRL); > + rdmsrl(MSR_IA32_SPEC_CTRL, tmp); > + tmp |= SPEC_CTRL_PSFD; > + x86_spec_ctrl_base |= tmp; > + wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); > + } > + > + return 0; > +} Shouldn't X86_FEATURE_MSR_SPEC_CTRL always be set if the CPU has X86_FEATURE_PSFD even if the new kernel parameter is not used ? (e.g. set X86_FEATURE_MSR_SPEC_CTRL in init_speculation_control() and have psf_cmdline() do the rest) Considering KVM/virtualization for a CPU that has X86_FEATURE_PSFD but no other existing feature with MSR_IA32_SPEC_CTRL, if a host doesn't enable PSFD with the new parameter, the host doesn't have X86_FEATURE_MSR_SPEC_CTRL. Then, it would be a problem if its guests want to use PSFD looking at x86_virt_spec_ctrl(). (I'm not sure how you will change your previous KVM patch though) Thanks, Reiji