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 35607C433E0 for ; Wed, 17 Mar 2021 21:20:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D946064EEE for ; Wed, 17 Mar 2021 21:20:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231725AbhCQVTg (ORCPT ); Wed, 17 Mar 2021 17:19:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59136 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230369AbhCQVTf (ORCPT ); Wed, 17 Mar 2021 17:19:35 -0400 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F681C06174A for ; Wed, 17 Mar 2021 14:19:35 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id g10so203000plt.8 for ; Wed, 17 Mar 2021 14:19:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=ZCl7wm+rg+7YdxDRvddMtggI/CCto6o7F3c4jWSDx1s=; b=K991Jlgq3FuxzlY2VOYfCRhMGNagbKqPw1F818Bqfjk9Lf1hCAlStw1xaDZV8H9/aS BA7JScOMgoxv/B9y6pbQ6ixojP0HkhRuf/wyCrCUnYaQI8+saOu9sSKGIC68JG/0CB3K HJO+mhSj/6uey96LussfTTk68eT8Iv+8rkq4D57Q8/Pa6UaweTc+GsbzLJWrrlmKuI2o 1zQyiv0jz9hobn2/8MiYK7xiG6GvpOCI7i+8zTajdzTzEX1UxFCwkGdlDtSx+9nFdstM iug3BNi1hMfc5EjJSp3+jGIc+RMK87AGPodEPpm0EFz0yYD+/z3ctzkzQ3MnddB+yryw Dotw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=ZCl7wm+rg+7YdxDRvddMtggI/CCto6o7F3c4jWSDx1s=; b=B+sz3Aw85p7gL4oM74v0409AoDBdY/Ppbra0s13xEJW+HrF2WfS3Y+kwiXs9OBdUL0 sMR4p/Z8L2slCQw0yjpqRjZy7lKeSZkg95MHUkpG+ObPnvyvvHapqu+uILcv9nxxgI6B b22ksfK32/byrCWJD3oipqZtTZgWnXq3wOTdX4l9GFI0RDXpk4LrQeCXXgH54ab8amD0 A1PU8ioJPscOdcROXJbDBDQmU3Ra4LyjA2VQkP47AIUdc9jUCdjnUcdlE3LKupZS8tH0 Lck6S13tyo1vnZAlQMPXar1ugIHd72RqMr9YHGIDSBS+lFvjRm9WIwciqvNcx/tH8Y7X c05A== X-Gm-Message-State: AOAM530+DUBq4o8BMIRFe+5iJ25qq/Idk10+2J55tKhpH7ciMlEjg7w2 C+YLIimr1CyURym+GCTr/DOJ0Q== X-Google-Smtp-Source: ABdhPJyujNquT6pOn2lBA3SU/ja5oES6AA9+IQBQdZCbEmuJ8JH7+Y+2X0MY/+6PYQs893ANp2QqOQ== X-Received: by 2002:a17:90a:db51:: with SMTP id u17mr788836pjx.194.1616015974590; Wed, 17 Mar 2021 14:19:34 -0700 (PDT) Received: from google.com ([2620:15c:f:10:e113:95c2:2d1:e304]) by smtp.gmail.com with ESMTPSA id iq6sm59012pjb.31.2021.03.17.14.19.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Mar 2021 14:19:33 -0700 (PDT) Date: Wed, 17 Mar 2021 14:19:27 -0700 From: Sean Christopherson To: Borislav Petkov Cc: Thomas Gleixner , Ingo Molnar , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, Joerg Roedel , Tom Lendacky , Brijesh Singh , Peter Gonda Subject: Re: [PATCH] x86/cpu/AMD: Adjust x86_phys_bits to account for reduced PA in SEV-* guests Message-ID: References: <20210317183243.2904919-1-seanjc@google.com> <20210317191132.GD25069@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 17, 2021, Sean Christopherson wrote: > On Wed, Mar 17, 2021, Borislav Petkov wrote: > > IOW, you have c_bit so your valid address space is [0 .. c_bit-1] no? > > I haven't found anything in the GHCB that dictates that MAXPHYADDR == C_BIT-1, > or more specifically that MAXPHYADDR == C_BIT - PhysAddrReduction. E.g. AFAICT, > a VMM could do C_BIT=47, MAXPHYADDR=36, PhysAddrReduction=0, and that would be > allowed by the GHCB. > > Forcing "c->x86_phys_bits = c_bit - 1" doesn't seem like it would break anything, > but it's also technically wrong. On the other hand, "C_BIT=47, MAXPHYADDR=36, PhysAddrReduction=0" would mean the C-bit is an illegal PA bit from the guest's perspective. That's rather nonsensical, but also not technically disallowed by the APM or GHCB specs.