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 66B93EB64DA for ; Fri, 30 Jun 2023 21:49:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232314AbjF3VtV (ORCPT ); Fri, 30 Jun 2023 17:49:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229519AbjF3VtT (ORCPT ); Fri, 30 Jun 2023 17:49:19 -0400 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0EB130F7 for ; Fri, 30 Jun 2023 14:49:18 -0700 (PDT) Received: by mail-pj1-x104a.google.com with SMTP id 98e67ed59e1d1-262e2cb725eso2132525a91.0 for ; Fri, 30 Jun 2023 14:49:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1688161758; x=1690753758; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=zTUka4vChlAMOHcpVhHgty9kj/qOPTWJd50kkZc81hM=; b=rHvFl4koS/Nebfb5q2rMzvlY3IzPjKCLC0q3nL4OZsNyKj7mRpsyhSWRkRZGdxuElJ a2w2GAHr5L1wtRqX6PVfNEH1G9dvLp7nm3FQ1+i2utLNjdsc8K/eumgNMk8kroYqvpFj zJ64Z89YSeQNwW/SRmPISAe7I9EtWem3EXJKH+VEbxEDJJsYpTU6kkbi8QjcNuzB90r7 G3FqYjOeG42HYyqBU/pN7sLEpeuIxvKV9M3MvqGh6cMR/eda7bRt5LvX7sOc4oh+WB3f 1mT259bNfSuPFIHRJaQqsvVFkTnrBpJR3Mn9v3CKxcbGZzS2GxO+z7GYPtZQ4IkOYyzm N3qQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688161758; x=1690753758; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=zTUka4vChlAMOHcpVhHgty9kj/qOPTWJd50kkZc81hM=; b=SQyuCbIvLGhSJDBXV9VsP7wmVWDGKLajLoKlytJ5iFJ587DSmWeoX8KMTgGlDj0I5R devh/GpyCarwBgmAO7qOAEsLdf4Sr0SokqD47cttTNVFyCYwTyZVu3/x0SaNrnl7VB1R vA/3KyCcC5Gb9/jxdQnqUniDlHWydrl0jTcHboFKx7/g3NQe3lZHO0gpf6daQb5DA46Z 6ziNGUzsU6TSxEGepvkSx/T+fRGVfwsIUD1mSJRhHTppYeAqhCWztsOXXKBH7qUhWmxm qwGuECZJD7AVJlRt02HHjDc35V2M3Iw0qGPjdJI1lDq/bpIE+H+R0H4gIIMaGzHrhhoa Utxg== X-Gm-Message-State: AC+VfDzkS3prvVuLAJcGGk2OB/Y7s8S4VNKsT8bAXfoSkyDIt+2DwjSx vROeYB4hxkVhmc7IYHU5F5gwvdXFPeE= X-Google-Smtp-Source: ACHHUZ5HGnnUm8T1L1VacYYEQr/B4a0MtvpWAOIX8lbADrvRgJAvGdTHeJduKXjuDdP6rFPrOM+5e8UM5YI= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90b:3c03:b0:25e:cd8e:e85b with SMTP id pb3-20020a17090b3c0300b0025ecd8ee85bmr4235323pjb.1.1688161758313; Fri, 30 Jun 2023 14:49:18 -0700 (PDT) Date: Fri, 30 Jun 2023 14:49:16 -0700 In-Reply-To: <20230615063757.3039121-6-aik@amd.com> Mime-Version: 1.0 References: <20230615063757.3039121-1-aik@amd.com> <20230615063757.3039121-6-aik@amd.com> Message-ID: Subject: Re: [PATCH kernel 5/9] KVM: SVM/SEV/SEV-ES: Rework intercepts From: Sean Christopherson To: Alexey Kardashevskiy Cc: kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Tom Lendacky , Santosh Shukla Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Jun 15, 2023, Alexey Kardashevskiy wrote: > @@ -2976,6 +2977,16 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm) > svm_set_intercept(svm, TRAP_CR4_WRITE); > svm_set_intercept(svm, TRAP_CR8_WRITE); > > + /* > + * DR7 access must remain intercepted for an SEV-ES guest to disallow > + * the guest kernel set up a #DB on memory that's needed to vector a #DB > + * as otherwise the CPU gets stuck in an infinite #DB loop. > + */ This isn't correct. Letting the guest configuring breakpoints would be weird and nonsensical, but it wouldn't lead to infinite #DBs so long as KVM intercepts #DB. KVM intercepts DR7 when DebugSwap isn't enabled because otherwise KVM has no way of context switching DR[0-3] for the guest. At least, I assume that's the case, AFAICT the APM never actually says what happens with DR[0-3] when DebugSwap is disabled.