Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752291AbdLLJ4P (ORCPT ); Tue, 12 Dec 2017 04:56:15 -0500 Received: from mail-ot0-f195.google.com ([74.125.82.195]:44062 "EHLO mail-ot0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbdLLJ4H (ORCPT ); Tue, 12 Dec 2017 04:56:07 -0500 X-Google-Smtp-Source: ACJfBosfpjTnSvtL7nbpK7tt7oTbNpkW0DSZC2tAFNNqMSBf3+b2RyglrEIvIHaJQ+xQhl5XF2npmBSvLsI9fP209Ng= MIME-Version: 1.0 In-Reply-To: References: <1512942265-40606-1-git-send-email-wanpeng.li@hotmail.com> <47429484-71b1-6c42-74e0-af2fd7dfb5c5@redhat.com> From: Wanpeng Li Date: Tue, 12 Dec 2017 17:56:06 +0800 Message-ID: Subject: Re: [PATCH RESEND] KVM: X86: Fix load bad host fpu state To: David Hildenbrand Cc: "linux-kernel@vger.kernel.org" , kvm , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li , Rik van Riel , "# v3 . 10+" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id vBC9uJTg007231 Content-Length: 3126 Lines: 78 2017-12-12 17:40 GMT+08:00 David Hildenbrand : > On 11.12.2017 22:51, Wanpeng Li wrote: >> 2017-12-12 4:48 GMT+08:00 David Hildenbrand : >>> 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. >> >> There is a warning in fpu__initialize() which results in just >> current->thread.fpu can take advantage of. > > Wonder if it would make more sense to > > a) drop the WARN > b) introduce a new variant without the WARN (the existing one can call this) > > Manual initialization looks ugly. How about this? https://lkml.org/lkml/2017/12/12/5 Regards, Wanpeng Li