From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:33846) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gn6jY-0001gk-LR for qemu-devel@nongnu.org; Fri, 25 Jan 2019 14:01:45 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gn6jX-0001gV-Pw for qemu-devel@nongnu.org; Fri, 25 Jan 2019 14:01:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55374) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gn6jX-0001fH-KB for qemu-devel@nongnu.org; Fri, 25 Jan 2019 14:01:43 -0500 From: Eduardo Habkost Date: Fri, 25 Jan 2019 17:01:34 -0200 Message-Id: <20190125190134.25492-1-ehabkost@redhat.com> Subject: [Qemu-devel] [PATCH] i386: Disable MSR_PLATFORM_INFO emulation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , Maxime Coquelin , kvm@vger.kernel.org, Eduardo Habkost , Richard Henderson , Marcelo Tosatti Linux v4.12 introduced[1] emulation of MSR_PLATFORM_INFO and MSR_MISC_FEATURES_ENABLES, and enabled the MSR_PLATFORM_INFO_CPUID_FAULT bit unconditionally. This made guests incorrectly believe the VM emulates MSR_MISC_FEATURES_ENABLES properly (which is not true because QEMU has no migration code to handle the MSR). The KVM_CAP_MSR_PLATFORM_INFO capability was added[2] to Linux v4.19 to address the issue. Use it to disable emulation of MSR_PLATFORM_INFO and stop incorrectly exposing cpuid_fault to guests. References: [1] commit db2336a80489 ("KVM: x86: virtualize cpuid faulting") [2] commit 6fbbde9a1969 ("KVM: x86: Control guest reads of MSR_PLATFORM_INFO") Reported-by: Maxime Coquelin Signed-off-by: Eduardo Habkost --- target/i386/kvm.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/target/i386/kvm.c b/target/i386/kvm.c index 9af4542fb8..9629f25c90 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -1647,6 +1647,14 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } + /* + * QEMU doesn't initialize MSR_PLATFORM_INFO yet, so disable the MSR + * unconditionally until support for the MSR is properly implemented + */ + if (kvm_check_extension(s, KVM_CAP_MSR_PLATFORM_INFO)) { + kvm_vm_enable_cap(s, KVM_CAP_MSR_PLATFORM_INFO, 0); + } + return 0; } -- 2.18.0.rc1.1.g3f1ff2140