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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 92FADC432C0 for ; Tue, 3 Dec 2019 23:24:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5DC352068E for ; Tue, 3 Dec 2019 23:24:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nwzlrdoT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727047AbfLCXYN (ORCPT ); Tue, 3 Dec 2019 18:24:13 -0500 Received: from mail-il1-f195.google.com ([209.85.166.195]:38292 "EHLO mail-il1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726534AbfLCXYN (ORCPT ); Tue, 3 Dec 2019 18:24:13 -0500 Received: by mail-il1-f195.google.com with SMTP id u17so4881851ilq.5 for ; Tue, 03 Dec 2019 15:24:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=snfgGor+TmMvyRLPPsOqMsn204mo1+lOHUtWuYXLS9o=; b=nwzlrdoTu49v+A1Gk007cwFAmGonL2uTl7dlK7XrX6b9UwjT1SAI9FYWvohWpgTe85 U97hV2R3yF5mvWMzcmhc/uY490WImQp8k4ZTlNMZId9qa4UOlsj7FuCxQ4rS8Nyhn57U rgE35JU5t9ADet3vw4KZjhRiZUPazxniKQ2yx4NIn0c0azToAUA4AeRhFt2M5LS9gnUp Yg1+r242jKEnMn7LA4VFsmrKLTsdmnXGd5lzktXYAfJiuC7KFB40fKeiJC8qCjASEnu8 ZHraSqJib9jr5KSJCu6jfcJeXQL/u+d/Ue4aP+iwTDIy2jNiRlYoXmrnP9XUOfGwpUhp 00lw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=snfgGor+TmMvyRLPPsOqMsn204mo1+lOHUtWuYXLS9o=; b=UqF9Z/YfxQ+i2uPC+zVCng0DnC2WpdGy/PEfVLq0Iv21jskX4AOVnw9KteMsLckMea OGPsPVY48SThimvYPRYm9xg+EvTbVQzla6ujCqZnxP33IugVuIs1YushwAso6PVtHD/t 0LWudEwPpp0zwkrqwEgCuHRmCjAFgDqvIprDBqlGmYDbLt9MrN/xIoX2GaiGZQ9ZzsT5 ErJEUA8hdeilzRys5oVCdF75s0DSzQBmW4HO9gFNEu5HwbZWaRuKU7A32akEFardtfh8 xxZFraShudHuifae8ECGHm13lTF1A5CWs98UDePZNEtGj0uWufmLldJdccBs5WEgCcXl TwvQ== X-Gm-Message-State: APjAAAWcif2chYMbhFS3d6ioSDlFd5EyIleLTjZxamPpqSgx3cDnhKlw tvhFe2zH7tSMgweYI9DrxCRdlkkmeEU7Xjj2YR8Cv8ddzhHbYQ== X-Google-Smtp-Source: APXvYqzKF6ktCBSGoWNa1tGRgNtNv3ytG1vtIyZvmgmOuCICcNb14tVgA45017FKdAax35ZaKyqcqF2/NBcn5dSfT5c= X-Received: by 2002:a92:8983:: with SMTP id w3mr850389ilk.108.1575415451753; Tue, 03 Dec 2019 15:24:11 -0800 (PST) MIME-Version: 1.0 References: <20191203210825.26827-1-jmattson@google.com> <20191203225918.GO19877@linux.intel.com> In-Reply-To: <20191203225918.GO19877@linux.intel.com> From: Jim Mattson Date: Tue, 3 Dec 2019 15:24:00 -0800 Message-ID: Subject: Re: [PATCH] kvm: vmx: Stop wasting a page for guest_msrs To: Sean Christopherson Cc: kvm list Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Dec 3, 2019 at 2:59 PM Sean Christopherson wrote: > > 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. Instead of setup_msrs(), what if I add that BUILD_BUG_ON() in vmx_create_vcpu(), where I'm getting rid of the old BUILD_BUG_ON() regarding ARRAY_SIZE(vmx_msr_index)? > > #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 > >