Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752926AbdCNUay (ORCPT ); Tue, 14 Mar 2017 16:30:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36442 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752804AbdCNUaw (ORCPT ); Tue, 14 Mar 2017 16:30:52 -0400 Date: Tue, 14 Mar 2017 21:30:43 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: David Hildenbrand Cc: kvm@vger.kernel.org, Paolo Bonzini , dvyukov@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] KVM: VMX: drop vmm_exclusive module parameter Message-ID: <20170314203042.GB5435@potion> References: <20170310114713.7571-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170310114713.7571-1-david@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 14 Mar 2017 20:30:47 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4689 Lines: 138 2017-03-10 12:47+0100, David Hildenbrand: > vmm_exclusive=0 leads to KVM setting X86_CR4_VMXE always and calling > VMXON only when the vcpu is loaded. X86_CR4_VMXE is used as an > indication in cpu_emergency_vmxoff() (called on kdump) if VMXOFF has to be > called. This is obviously not the case if both are used independtly. > Calling VMXOFF without a previous VMXON will result in an exception. > > In addition, X86_CR4_VMXE is used as a mean to test if VMX is already in > use by another VMM in hardware_enable(). So there can't really be > co-existance. If the other VMM is prepared for co-existance and does a > similar check, only one VMM can exist. If the other VMM is not prepared > and blindly sets/clears X86_CR4_VMXE, we will get inconsistencies with > X86_CR4_VMXE. > > As we also had bug reports related to clearing of vmcs with vmm_exclusive=0 > this seems to be pretty much untested. So let's better drop it. Totally, Reviewed-by: Radim Krčmář > While at it, directly move setting/clearing X86_CR4_VMXE into > kvm_cpu_vmxon/off. > > Signed-off-by: David Hildenbrand > --- > arch/x86/kvm/vmx.c | 38 +++++++------------------------------- > 1 file changed, 7 insertions(+), 31 deletions(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 283aa86..bbbfe12 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -84,9 +84,6 @@ module_param_named(eptad, enable_ept_ad_bits, bool, S_IRUGO); > static bool __read_mostly emulate_invalid_guest_state = true; > module_param(emulate_invalid_guest_state, bool, S_IRUGO); > > -static bool __read_mostly vmm_exclusive = 1; > -module_param(vmm_exclusive, bool, S_IRUGO); > - > static bool __read_mostly fasteoi = 1; > module_param(fasteoi, bool, S_IRUGO); > > @@ -914,8 +911,6 @@ static void nested_release_page_clean(struct page *page) > > static unsigned long nested_ept_get_cr3(struct kvm_vcpu *vcpu); > static u64 construct_eptp(unsigned long root_hpa); > -static void kvm_cpu_vmxon(u64 addr); > -static void kvm_cpu_vmxoff(void); > static bool vmx_xsaves_supported(void); > static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr); > static void vmx_set_segment(struct kvm_vcpu *vcpu, > @@ -2235,15 +2230,10 @@ static void decache_tsc_multiplier(struct vcpu_vmx *vmx) > static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > - u64 phys_addr = __pa(per_cpu(vmxarea, cpu)); > bool already_loaded = vmx->loaded_vmcs->cpu == cpu; > > - if (!vmm_exclusive) > - kvm_cpu_vmxon(phys_addr); > - else if (!already_loaded) > - loaded_vmcs_clear(vmx->loaded_vmcs); > - > if (!already_loaded) { > + loaded_vmcs_clear(vmx->loaded_vmcs); > local_irq_disable(); > crash_disable_local_vmclear(cpu); > > @@ -2321,11 +2311,6 @@ static void vmx_vcpu_put(struct kvm_vcpu *vcpu) > vmx_vcpu_pi_put(vcpu); > > __vmx_load_host_state(to_vmx(vcpu)); > - if (!vmm_exclusive) { > - __loaded_vmcs_clear(to_vmx(vcpu)->loaded_vmcs); > - vcpu->cpu = -1; > - kvm_cpu_vmxoff(); > - } > } > > static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu); > @@ -3416,6 +3401,7 @@ static __init int vmx_disabled_by_bios(void) > > static void kvm_cpu_vmxon(u64 addr) > { > + cr4_set_bits(X86_CR4_VMXE); > intel_pt_handle_vmx(1); > > asm volatile (ASM_VMX_VMXON_RAX > @@ -3458,12 +3444,8 @@ static int hardware_enable(void) > /* enable and lock */ > wrmsrl(MSR_IA32_FEATURE_CONTROL, old | test_bits); > } > - cr4_set_bits(X86_CR4_VMXE); > - > - if (vmm_exclusive) { > - kvm_cpu_vmxon(phys_addr); > - ept_sync_global(); > - } > + kvm_cpu_vmxon(phys_addr); > + ept_sync_global(); > > native_store_gdt(this_cpu_ptr(&host_gdt)); > > @@ -3489,15 +3471,13 @@ static void kvm_cpu_vmxoff(void) > asm volatile (__ex(ASM_VMX_VMXOFF) : : : "cc"); > > intel_pt_handle_vmx(0); > + cr4_clear_bits(X86_CR4_VMXE); > } > > static void hardware_disable(void) > { > - if (vmm_exclusive) { > - vmclear_local_loaded_vmcss(); > - kvm_cpu_vmxoff(); > - } > - cr4_clear_bits(X86_CR4_VMXE); > + vmclear_local_loaded_vmcss(); > + kvm_cpu_vmxoff(); > } > > static __init int adjust_vmx_controls(u32 ctl_min, u32 ctl_opt, > @@ -9228,11 +9208,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) > vmx->loaded_vmcs->shadow_vmcs = NULL; > if (!vmx->loaded_vmcs->vmcs) > goto free_msrs; > - if (!vmm_exclusive) > - kvm_cpu_vmxon(__pa(per_cpu(vmxarea, raw_smp_processor_id()))); > loaded_vmcs_init(vmx->loaded_vmcs); > - if (!vmm_exclusive) > - kvm_cpu_vmxoff(); > > cpu = get_cpu(); > vmx_vcpu_load(&vmx->vcpu, cpu); > -- > 2.9.3 >