From patchwork Thu Mar 21 19:35:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eduardo Habkost X-Patchwork-Id: 1060418 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 44QH9d5gnSz9sRy for ; Fri, 22 Mar 2019 06:37:08 +1100 (AEDT) Received: from localhost ([127.0.0.1]:45723 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h73Ut-000303-Lu for incoming@patchwork.ozlabs.org; Thu, 21 Mar 2019 15:37:03 -0400 Received: from eggs.gnu.org ([209.51.188.92]:58698) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h73U4-0002zj-Sp for qemu-devel@nongnu.org; Thu, 21 Mar 2019 15:36:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h73U3-0006Zr-Vy for qemu-devel@nongnu.org; Thu, 21 Mar 2019 15:36:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47646) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1h73U3-0006YE-Js for qemu-devel@nongnu.org; Thu, 21 Mar 2019 15:36:11 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D6CFA7E42E; Thu, 21 Mar 2019 19:36:10 +0000 (UTC) Received: from localhost (ovpn-116-26.gru2.redhat.com [10.97.116.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6710D5D9D6; Thu, 21 Mar 2019 19:36:10 +0000 (UTC) From: Eduardo Habkost To: Peter Maydell , qemu-devel@nongnu.org Date: Thu, 21 Mar 2019 16:35:56 -0300 Message-Id: <20190321193600.15935-2-ehabkost@redhat.com> In-Reply-To: <20190321193600.15935-1-ehabkost@redhat.com> References: <20190321193600.15935-1-ehabkost@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Thu, 21 Mar 2019 19:36:10 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 1/5] i386: kvm: Disable arch_capabilities if MSR can't be set X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Eduardo Habkost , Richard Henderson Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" KVM has two bugs in the handling of MSR_IA32_ARCH_CAPABILITIES: 1) Linux commit commit 1eaafe91a0df ("kvm: x86: IA32_ARCH_CAPABILITIES is always supported") makes GET_SUPPORTED_CPUID return arch_capabilities even if running on SVM. This makes "-cpu host,migratable=off" incorrectly expose arch_capabilities on CPUID on AMD hosts (where the MSR is not emulated by KVM). 2) KVM_GET_MSR_INDEX_LIST does not return MSR_IA32_ARCH_CAPABILITIES if the MSR is not supported by the host CPU. This makes QEMU not initialize the MSR properly at kvm_put_msrs() on those hosts. Work around both bugs on the QEMU side, by checking if the MSR was returned by KVM_GET_MSR_INDEX_LIST before returning the feature flag on kvm_arch_get_supported_cpuid(). This has the unfortunate side effect of making arch_capabilities unavailable on hosts without hardware support for the MSR until bug #2 is fixed on KVM, but I can't see another way to work around bug #1 without that side effect. Signed-off-by: Eduardo Habkost Message-Id: <20190125220606.4864-2-ehabkost@redhat.com> Signed-off-by: Eduardo Habkost --- target/i386/kvm.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/target/i386/kvm.c b/target/i386/kvm.c index beae1b99da..3b29ce5c0d 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -389,6 +389,15 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function, if (host_tsx_blacklisted()) { ret &= ~(CPUID_7_0_EBX_RTM | CPUID_7_0_EBX_HLE); } + } else if (function == 7 && index == 0 && reg == R_EDX) { + /* + * Linux v4.17-v4.20 incorrectly return ARCH_CAPABILITIES on SVM hosts. + * We can detect the bug by checking if MSR_IA32_ARCH_CAPABILITIES is + * returned by KVM_GET_MSR_INDEX_LIST. + */ + if (!has_msr_arch_capabs) { + ret &= ~CPUID_7_0_EDX_ARCH_CAPABILITIES; + } } else if (function == 0x80000001 && reg == R_ECX) { /* * It's safe to enable TOPOEXT even if it's not returned by