From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C123C43215 for ; Tue, 3 Dec 2019 22:59:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46CC220803 for ; Tue, 3 Dec 2019 22:59:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730773AbfLCW7V (ORCPT ); Tue, 3 Dec 2019 17:59:21 -0500 Received: from mga06.intel.com ([134.134.136.31]:2412 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730136AbfLCW7U (ORCPT ); Tue, 3 Dec 2019 17:59:20 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Dec 2019 14:59:19 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,275,1571727600"; d="scan'208";a="412367145" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by fmsmga006.fm.intel.com with ESMTP; 03 Dec 2019 14:59:19 -0800 Date: Tue, 3 Dec 2019 14:59:18 -0800 From: Sean Christopherson To: Jim Mattson Cc: kvm@vger.kernel.org Subject: Re: [PATCH] kvm: vmx: Stop wasting a page for guest_msrs Message-ID: <20191203225918.GO19877@linux.intel.com> References: <20191203210825.26827-1-jmattson@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191203210825.26827-1-jmattson@google.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Dec 03, 2019 at 01:08:25PM -0800, Jim Mattson wrote: > We will never need more guest_msrs than there are indices in > vmx_msr_index. Thus, at present, the guest_msrs array will not exceed > 168 bytes. > > Signed-off-by: Jim Mattson > --- > arch/x86/kvm/vmx/vmx.c | 14 ++------------ > arch/x86/kvm/vmx/vmx.h | 8 +++++++- > 2 files changed, 9 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 1b9ab4166397d..0b3c7524456f1 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -443,7 +443,7 @@ static unsigned long host_idt_base; > * support this emulation, IA32_STAR must always be included in > * vmx_msr_index[], even in i386 builds. > */ > -const u32 vmx_msr_index[] = { > +const u32 vmx_msr_index[NR_GUEST_MSRS] = { What if we keep this as is and add BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) != NR_SHARED_MSRS); in setup_msrs()? That way the build will fail if someone adds an MSR but forgets to update the #define. With this change, gcc only spits out a warning if the number of elements exceeds the size of the array and presumably drops the extra elements on the floor. > #ifdef CONFIG_X86_64 > MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR, > #endif > @@ -6666,7 +6666,6 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu) > free_vpid(vmx->vpid); > nested_vmx_free_vcpu(vcpu); > free_loaded_vmcs(vmx->loaded_vmcs); > - kfree(vmx->guest_msrs); > kvm_vcpu_uninit(vcpu); > kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu); > kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu); > @@ -6723,13 +6722,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) > goto uninit_vcpu; > } > > - vmx->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL_ACCOUNT); > - BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) * sizeof(vmx->guest_msrs[0]) > - > PAGE_SIZE); > - > - if (!vmx->guest_msrs) > - goto free_pml; > - > for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) { > u32 index = vmx_msr_index[i]; > u32 data_low, data_high; > @@ -6760,7 +6752,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) > > err = alloc_loaded_vmcs(&vmx->vmcs01); > if (err < 0) > - goto free_msrs; > + goto free_pml; > > msr_bitmap = vmx->vmcs01.msr_bitmap; > vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, MSR_TYPE_R); > @@ -6822,8 +6814,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) > > free_vmcs: > free_loaded_vmcs(vmx->loaded_vmcs); > -free_msrs: > - kfree(vmx->guest_msrs); > free_pml: > vmx_destroy_pml_buffer(vmx); > uninit_vcpu: > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h > index 7c1b978b2df44..08bc24fa59909 100644 > --- a/arch/x86/kvm/vmx/vmx.h > +++ b/arch/x86/kvm/vmx/vmx.h > @@ -22,6 +22,12 @@ extern u32 get_umwait_control_msr(void); > > #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4)) > > +#ifdef CONFIG_X86_64 > +#define NR_GUEST_MSRS 7 > +#else > +#define NR_GUEST_MSRS 4 > +#endif As much as I hate the "shared msrs" terminology, "guest msrs" is even more confusing and misleading. NR_SHARED_MSRS? > + > #define NR_LOADSTORE_MSRS 8 > > struct vmx_msrs { > @@ -206,7 +212,7 @@ struct vcpu_vmx { > u32 idt_vectoring_info; > ulong rflags; > > - struct shared_msr_entry *guest_msrs; > + struct shared_msr_entry guest_msrs[NR_GUEST_MSRS]; > int nmsrs; > int save_nmsrs; > bool guest_msrs_ready; > -- > 2.24.0.393.g34dc348eaf-goog >