From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967108AbeEYQG1 (ORCPT ); Fri, 25 May 2018 12:06:27 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:41488 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S966464AbeEYQG0 (ORCPT ); Fri, 25 May 2018 12:06:26 -0400 From: Vitaly Kuznetsov To: Arnd Bergmann Cc: Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Lan Tianyu , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Jim Mattson , Wanpeng Li , David Hildenbrand , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: VMX: fix building without CONFIG_HYPERV References: <20180525153640.3228067-1-arnd@arndb.de> Date: Fri, 25 May 2018 18:06:18 +0200 In-Reply-To: <20180525153640.3228067-1-arnd@arndb.de> (Arnd Bergmann's message of "Fri, 25 May 2018 17:36:17 +0200") Message-ID: <87d0xjwwhx.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Arnd Bergmann writes: > The global ms_hyperv variable is part of the hyperv support, so > we get a link error from accessing it in kernels that have this > turned off: > > arch/x86/kvm/vmx.o: In function `alloc_loaded_vmcs': > vmx.c:(.text+0x1654a): undefined reference to `ms_hyperv' > vmx.c:(.text+0x1657a): undefined reference to `ms_hyperv' > > This changes the condition to first check the compile-time > configuration symbol to avoid the link error. > > Fixes: ceef7d10dfb6 ("KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support") > Signed-off-by: Arnd Bergmann Thanks, Reviewed-by: Vitaly Kuznetsov (I don't really like this IS_ENABLED(CONFIG_HYPERV) spreading across KVM but keeping stuff like this ms_hyperv structure defined when !IS_ENABLED(CONFIG_HYPERV) is also ugly. It may make sense to define helpers similar to kvm_para_has_feature() and define them to 'false' when Hyper-V support code is compiled out. I'll look into this option later, this patch should be taken to fix the immediate issue). > --- > arch/x86/kvm/vmx.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index ea098131dcce..e6d6ccab43c3 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -4232,7 +4232,8 @@ static int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs) > goto out_vmcs; > memset(loaded_vmcs->msr_bitmap, 0xff, PAGE_SIZE); > > - if (static_branch_unlikely(&enable_evmcs) && > + if (IS_ENABLED(CONFIG_HYPERV) && > + static_branch_unlikely(&enable_evmcs) && > (ms_hyperv.nested_features & HV_X64_NESTED_MSR_BITMAP)) { > struct hv_enlightened_vmcs *evmcs = > (struct hv_enlightened_vmcs *)loaded_vmcs->vmcs; -- Vitaly