Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752175AbdLKVvb (ORCPT ); Mon, 11 Dec 2017 16:51:31 -0500 Received: from mail-ot0-f193.google.com ([74.125.82.193]:44021 "EHLO mail-ot0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbdLKVv1 (ORCPT ); Mon, 11 Dec 2017 16:51:27 -0500 X-Google-Smtp-Source: ACJfBotKdGwNM0S+b8h7yN8nIfyRLScOi3as1M7p3eygcK91Zk8dab0u1tfosyVDcd7QmQ4k3D1cqHN7FHajbtKv/C0= MIME-Version: 1.0 In-Reply-To: <47429484-71b1-6c42-74e0-af2fd7dfb5c5@redhat.com> 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 05:51:26 +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 vBBLpZLt009873 Content-Length: 2798 Lines: 72 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. > > E.g. can't we simply initialize that in kvm_load_guest_fpu? We still miss to initialize qemu user FPU context for the above calltrace. Regards, Wanpeng Li