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 39B4BC54EBC for ; Thu, 12 Jan 2023 12:14:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231588AbjALMOG (ORCPT ); Thu, 12 Jan 2023 07:14:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234994AbjALMNc (ORCPT ); Thu, 12 Jan 2023 07:13:32 -0500 Received: from mail-ed1-x536.google.com (mail-ed1-x536.google.com [IPv6:2a00:1450:4864:20::536]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8D11BBE for ; Thu, 12 Jan 2023 04:13:26 -0800 (PST) Received: by mail-ed1-x536.google.com with SMTP id c17so26516555edj.13 for ; Thu, 12 Jan 2023 04:13:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:sender :from:to:cc:subject:date:message-id:reply-to; bh=+rMbanEkiTZXC1SYY43oQzK0GtyNp4kNyLJCdJ4ttVo=; b=gb5LoMjBQ178DQnDa/b1ZWJaBlHi0qZhKJj2U5qZ1UwJQ/ywGgeNJ9AEsudC7FEXOy NxRY0bI1kPoUmutRRPZhVKVOJvbkkuFPL68E0j790LNh1zoIRSRrBIycl1FghYWxvj1s Vkeh3ixBUA2q6BRVm/qyE13r4cbaqQCWAQohQyjniA9eNthZ/FPld5ApwkMbf/s0BzAK OobIOnmfzzU+7XWasHTyQY477ccEs7j3CY74SiEjiueMbSXPO1LXQqV7PejOG+CJPE+9 2Uo99cPk87sQ+JvKS47bhqb3aEsnvOCT8g/e00MiXqu4MpX8ufGSFC8+YoE6oJIjXBXx Vk0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:sender :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=+rMbanEkiTZXC1SYY43oQzK0GtyNp4kNyLJCdJ4ttVo=; b=fHeCiCLNh4M9yitJmdKrJQeNbV6NGaNbWp+MtBD+9BZxNZ5Nwl4BJo95Nj04IE+C4n E9oulFL4Ufest0dduzklNnbn936wmDxwtUa0BiVDt6gn+2GQBqQd0UxLC6f576i4Xz2S S7YOk7HID6IRx0HCg17uBWXWCPZJ/a5dzrYCu/+62Fj2fpJJK2fYwbhIRJ2/PzLQ/eiT QcDW+oUspKmJfb+MQ7z5HkJ7AR7ffnxgAB+7dKJIw2dRhh5BXv32ZQws6MwcxhH+I1aW U7Sx3FC02dNbRmjr9uuuu+1uXLMKFIHDYQUpul4eTstw71LnTFrEJbzbgOyKAk04FR/k sPMw== X-Gm-Message-State: AFqh2kqoiniRh/49oGS7e/1SGXkCXVicBQx0szLlrsJmIOb9LV3tpHAO KGY0lwdxXXUsopuVXfrKT34= X-Google-Smtp-Source: AMrXdXv7ldueNqkwHFr4IF3a6zSirqNF5htYIuA6aY3PuA0cRchJEZEege9DqxASp4mXluWvFF3zHA== X-Received: by 2002:a05:6402:4015:b0:46a:3bd0:4784 with SMTP id d21-20020a056402401500b0046a3bd04784mr74535972eda.7.1673525604987; Thu, 12 Jan 2023 04:13:24 -0800 (PST) Received: from gmail.com ([31.46.242.235]) by smtp.gmail.com with ESMTPSA id s1-20020aa7d781000000b0048ecd372fc9sm7117071edq.2.2023.01.12.04.13.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Jan 2023 04:13:24 -0800 (PST) Sender: Ingo Molnar Date: Thu, 12 Jan 2023 13:13:20 +0100 From: Ingo Molnar To: Xin Li Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org, brgerst@gmail.com, chang.seok.bae@intel.com, jgross@suse.com Subject: Re: [PATCH v6 0/5] x86: Enable LKGS instruction Message-ID: References: <20230112072032.35626-1-xin3.li@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230112072032.35626-1-xin3.li@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Xin Li wrote: > LKGS instruction is introduced with Intel FRED (flexible return and event > delivery) specification. As LKGS is independent of FRED, we enable it as > a standalone CPU feature. > > LKGS behaves like the MOV to GS instruction except that it loads the base > address into the IA32_KERNEL_GS_BASE MSR instead of the GS segment’s > descriptor cache, which is exactly what Linux kernel does to load user > level GS base. Thus, with LKGS, there is no need to SWAPGS away from the > kernel GS base. Ok, this looks good to me. I've applied the first 4 patches to tip:x86/cpu, as the instruction exists in a public document and these patches are fine stand-alone as well, such as the factoring out of load_gs_index() methods from a high-use low level header into a new header file. Planning to apply the final, LKGS enabler patch as well, unless there's any objections from others? Thanks, Ingo