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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 3D61EC4363A for ; Tue, 20 Oct 2020 16:04:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9AA321534 for ; Tue, 20 Oct 2020 16:04:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="p+YTYFnA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437020AbgJTQEe (ORCPT ); Tue, 20 Oct 2020 12:04:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730985AbgJTQEe (ORCPT ); Tue, 20 Oct 2020 12:04:34 -0400 Received: from mail-il1-x142.google.com (mail-il1-x142.google.com [IPv6:2607:f8b0:4864:20::142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7DE5CC061755 for ; Tue, 20 Oct 2020 09:04:32 -0700 (PDT) Received: by mail-il1-x142.google.com with SMTP id j13so2982770ilc.4 for ; Tue, 20 Oct 2020 09:04:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=lNlB9YEedi1DCkSsmiZeDcO9zXDI+9cp+/wZCzJQVtc=; b=p+YTYFnA+0z42/OG9X9WFzK3kpkh4WHfxeFrEDCOSwHO8817IhHloUNnIupg+5494E TBLiuOljaVKtXEOt6ITyO/OsitEWd7ooSR1Y5VlrBd+0+Ssg2oJXCHfwH7ELDqtBZSM1 T3kl7gUhqegry/M+e5o8jLAXTC4EHUYlw2oZWx7HCgHhGvM7lYySl/sBHbjOM/yWylnZ xj21zhph2Fk2QRVH9qeIggTgenObMetcdesza8YNVN23AuLBeUpHiAFDgCQaK9mJw3k0 634Mgmds4tJeFsiR69fyDuK3qiDzH95h14GT8u5cTAcAOQ543/iTpRJyOFdyDuN/sQHk 118w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:date:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=lNlB9YEedi1DCkSsmiZeDcO9zXDI+9cp+/wZCzJQVtc=; b=cNV2jchP2u6j0CfmeGSkuMBs3UCUT4BGU2C+rbQQv0mtk9mK4tMM1JSY6liZLJHp4y em7e1tRp3lj/N8t77elenL/kkPYgEYcIVTINDhlaTGLxnX33/ozUq2KwaY5uQDo3sHu0 L3uQidZgnJxnABswfFs/bFWQbpC6SnXNnjPcLLjA5n8iAJ3D9zSZpTXlrbgbvrNg/MgQ rn7ZD2NoxQpqPHB/aH4V++FShloSQKlEPEtGfQPlGDu1T+Aexw1mTXpLgHnjy2mXYeIs 79hFLbqTRyD5BKXFuIBEAFIBAoaDhCOad7OJiiAWZ+HwIM5OYSXsPq4nNEriifCyPqqH DjnQ== X-Gm-Message-State: AOAM531lc5HgUBPSFkuuF2eM/Ixswetrpu/4GBWv/SctRQ09K0p0TEBA PlKwIpgJscPt/d0QJUWlBzM= X-Google-Smtp-Source: ABdhPJwXtQda0DLV083DLiaouxqH5RiPw+TsjqvllgYZzPUmjGoLQ31+BMrf27JAnmQLYg/w1UwQgw== X-Received: by 2002:a92:3007:: with SMTP id x7mr2689146ile.141.1603209871738; Tue, 20 Oct 2020 09:04:31 -0700 (PDT) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id f13sm2462907ilf.85.2020.10.20.09.04.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Oct 2020 09:04:30 -0700 (PDT) Sender: Arvind Sankar From: Arvind Sankar X-Google-Original-From: Arvind Sankar Date: Tue, 20 Oct 2020 12:04:28 -0400 To: Joerg Roedel Cc: Arvind Sankar , Joerg Roedel , x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Kees Cook , Martin Radev , Tom Lendacky , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/5] x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path Message-ID: <20201020160428.GA3233355@rani.riverdale.lan> References: <20201020121856.19427-1-joro@8bytes.org> <20201020121856.19427-4-joro@8bytes.org> <20201020141259.GC2996696@rani.riverdale.lan> <20201020154812.GB22179@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201020154812.GB22179@suse.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 20, 2020 at 05:48:12PM +0200, Joerg Roedel wrote: > On Tue, Oct 20, 2020 at 10:12:59AM -0400, Arvind Sankar wrote: > > On Tue, Oct 20, 2020 at 02:18:54PM +0200, Joerg Roedel wrote: > > Why use r10-r12 rather than the caller-save registers? Even for the head > > code where you need to perserve the cr3 value you can just return it in > > rax? > > It can surely be optimized, but it makes the code less robust. This > function is only called from assembly so the standard x86-64 calling > conventions might not be followed strictly. I think its better to make > as few assumptions as possible about the calling code to avoid > regressions. Changes to the head code are not necessarily tested with > SEV/SEV-ES guests by developers. > > Regards, > > Joerg This is called from both assembly and C, but anyway, you're already assuming r10 and r11 can be clobbered safely, and you just took out the save/restores in set_sev_encryption_mask, which is actually called only from assembly.