Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752160AbdLKUsP (ORCPT ); Mon, 11 Dec 2017 15:48:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36542 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbdLKUsI (ORCPT ); Mon, 11 Dec 2017 15:48:08 -0500 Subject: Re: [PATCH RESEND] KVM: X86: Fix load bad host fpu state To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li , Rik van Riel , stable@vger.kernel.org References: <1512942265-40606-1-git-send-email-wanpeng.li@hotmail.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <47429484-71b1-6c42-74e0-af2fd7dfb5c5@redhat.com> Date: Mon, 11 Dec 2017 21:48:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1512942265-40606-1-git-send-email-wanpeng.li@hotmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 11 Dec 2017 20:48:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2509 Lines: 75 On 10.12.2017 22:44, Wanpeng Li wrote: > From: Wanpeng Li > > ------------[ cut here ]------------ > Bad FPU state detected at kvm_put_guest_fpu+0xd8/0x2d0 [kvm], reinitializing FPU registers. > WARNING: CPU: 1 PID: 4594 at arch/x86/mm/extable.c:103 ex_handler_fprestore+0x88/0x90 > CPU: 1 PID: 4594 Comm: qemu-system-x86 Tainted: G B OE 4.15.0-rc2+ #10 > RIP: 0010:ex_handler_fprestore+0x88/0x90 > Call Trace: > fixup_exception+0x4e/0x60 > do_general_protection+0xff/0x270 > general_protection+0x22/0x30 > RIP: 0010:kvm_put_guest_fpu+0xd8/0x2d0 [kvm] > RSP: 0018:ffff8803d5627810 EFLAGS: 00010246 > kvm_vcpu_reset+0x3b4/0x3c0 [kvm] > kvm_apic_accept_events+0x1c0/0x240 [kvm] > kvm_arch_vcpu_ioctl_run+0x1658/0x2fb0 [kvm] > kvm_vcpu_ioctl+0x479/0x880 [kvm] > do_vfs_ioctl+0x142/0x9a0 > SyS_ioctl+0x74/0x80 > do_syscall_64+0x15f/0x600 > > This can be reproduced by running any testcase in kvm-unit-tests since > the qemu userspace FPU context is not initialized, which results in the > init path from kvm_apic_accept_events() will load/put qemu userspace > FPU context w/o initialized. In addition, w/o this splatting we still > should initialize vcpu->arch.user_fpu instead of current->thread.fpu. > This patch fixes it by initializing qemu user FPU context if it is > uninitialized before KVM_RUN. > > Cc: Paolo Bonzini > Cc: Radim Krčmář > Cc: Rik van Riel > Cc: stable@vger.kernel.org > Fixes: f775b13eedee (x86,kvm: move qemu/guest FPU switching out to vcpu_run) > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/x86.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index a92b22f..063a643 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -7273,10 +7273,13 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu) > > int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) > { > - struct fpu *fpu = ¤t->thread.fpu; > + struct fpu *fpu = &vcpu->arch.user_fpu; > int r; > > - fpu__initialize(fpu); > + if (!fpu->initialized) { > + fpstate_init(&fpu->state); > + fpu->initialized = 1; > + } Is there a chance of keeping using fpu__initialize() ? Duplicating the code is ugly. E.g. can't we simply initialize that in kvm_load_guest_fpu? > > kvm_sigset_activate(vcpu); > > -- Thanks, David / dhildenb