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 <rkrcmar@xxxxxxxxxx>
> While at it, directly move setting/clearing X86_CR4_VMXE into
> kvm_cpu_vmxon/off.
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
> 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
>
