From patchwork Tue Mar 5 16:42:03 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vitaly Kuznetsov X-Patchwork-Id: 13582732 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1B91AC54798 for ; Tue, 5 Mar 2024 16:48:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rhXxV-0006KU-Ha; Tue, 05 Mar 2024 11:48:08 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rhXxF-0006A3-UL for qemu-devel@nongnu.org; Tue, 05 Mar 2024 11:47:51 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rhXxD-0001ox-WD for qemu-devel@nongnu.org; Tue, 05 Mar 2024 11:47:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709657266; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AlBSI0rEWJpGFaPdh4aMHUVj52/YWrBZ2j7p6Ed+yGs=; b=TVotDujkAWq8mIEO/xTVQ9aHIgORZH3f4g7eQT6tR40g+2AXWcpmXh3eJxGFHUkIbuT96h RQwe960b7g13yxvHLmBq5TIWnr1b/V0r50TKV2iq5WNT+cHw43LpoimpIV81q43SKiAqn+ YBMu4hoaSC+Vqe/WYL+sxzEX1OHfnZQ= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-600-gBTjMl0tNXa2g2dop_zPSw-1; Tue, 05 Mar 2024 11:42:08 -0500 X-MC-Unique: gBTjMl0tNXa2g2dop_zPSw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5806428B6B22 for ; Tue, 5 Mar 2024 16:42:08 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.45.225.218]) by smtp.corp.redhat.com (Postfix) with ESMTP id BC8F84073486; Tue, 5 Mar 2024 16:42:07 +0000 (UTC) From: Vitaly Kuznetsov To: qemu-devel@nongnu.org, Paolo Bonzini Subject: [PATCH RESEND v3 2/3] i386: Exclude 'hv-syndbg' from 'hv-passthrough' Date: Tue, 5 Mar 2024 17:42:03 +0100 Message-ID: <20240305164204.525575-3-vkuznets@redhat.com> In-Reply-To: <20240305164204.525575-1-vkuznets@redhat.com> References: <20240305164204.525575-1-vkuznets@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=vkuznets@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.568, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Windows with Hyper-V role enabled doesn't boot with 'hv-passthrough' when no debugger is configured, this significantly limits the usefulness of the feature as there's no support for subtracting Hyper-V features from CPU flags at this moment (e.g. "-cpu host,hv-passthrough,-hv-syndbg" does not work). While this is also theoretically fixable, 'hv-syndbg' is likely very special and unneeded in the default set. Genuine Hyper-V doesn't seem to enable it either. Introduce 'skip_passthrough' flag to 'kvm_hyperv_properties' and use it as one-off to skip 'hv-syndbg' when enabling features in 'hv-passthrough' mode. Note, "-cpu host,hv-passthrough,hv-syndbg" can still be used if needed. As both 'hv-passthrough' and 'hv-syndbg' are debug features, the change should not have any effect on production environments. Signed-off-by: Vitaly Kuznetsov --- docs/system/i386/hyperv.rst | 13 +++++++++---- target/i386/kvm/kvm.c | 7 +++++-- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/docs/system/i386/hyperv.rst b/docs/system/i386/hyperv.rst index 2505dc4c86e0..009947e39141 100644 --- a/docs/system/i386/hyperv.rst +++ b/docs/system/i386/hyperv.rst @@ -262,14 +262,19 @@ Supplementary features ``hv-passthrough`` In some cases (e.g. during development) it may make sense to use QEMU in 'pass-through' mode and give Windows guests all enlightenments currently - supported by KVM. This pass-through mode is enabled by "hv-passthrough" CPU - flag. + supported by KVM. Note: ``hv-passthrough`` flag only enables enlightenments which are known to QEMU (have corresponding 'hv-' flag) and copies ``hv-spinlocks`` and ``hv-vendor-id`` values from KVM to QEMU. ``hv-passthrough`` overrides all other 'hv-' settings on - the command line. Also, enabling this flag effectively prevents migration as the - list of enabled enlightenments may differ between target and destination hosts. + the command line. + + Note: ``hv-passthrough`` does not enable ``hv-syndbg`` which can prevent certain + Windows guests from booting when used without proper configuration. If needed, + ``hv-syndbg`` can be enabled additionally. + + Note: ``hv-passthrough`` effectively prevents migration as the list of enabled + enlightenments may differ between target and destination hosts. ``hv-enforce-cpuid`` By default, KVM allows the guest to use all currently supported Hyper-V diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index f067e35d35b1..f01d19ad2d51 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -823,6 +823,7 @@ static struct { uint32_t bits; } flags[2]; uint64_t dependencies; + bool skip_passthrough; } kvm_hyperv_properties[] = { [HYPERV_FEAT_RELAXED] = { .desc = "relaxed timing (hv-relaxed)", @@ -951,7 +952,8 @@ static struct { {.func = HV_CPUID_FEATURES, .reg = R_EDX, .bits = HV_FEATURE_DEBUG_MSRS_AVAILABLE} }, - .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED) + .dependencies = BIT(HYPERV_FEAT_SYNIC) | BIT(HYPERV_FEAT_RELAXED), + .skip_passthrough = true, }, [HYPERV_FEAT_MSR_BITMAP] = { .desc = "enlightened MSR-Bitmap (hv-emsr-bitmap)", @@ -1360,7 +1362,8 @@ bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp) * hv_build_cpuid_leaf() uses this info to build guest CPUIDs. */ for (feat = 0; feat < ARRAY_SIZE(kvm_hyperv_properties); feat++) { - if (hyperv_feature_supported(cs, feat)) { + if (hyperv_feature_supported(cs, feat) && + !kvm_hyperv_properties[feat].skip_passthrough) { cpu->hyperv_features |= BIT(feat); } }