Messages in this thread Patch in this message | | | Date | Wed, 6 Jul 2022 18:44:47 +0000 | From | Sean Christopherson <> | Subject | Re: [PATCH v2 15/28] KVM: VMX: Check CPU_BASED_{INTR,NMI}_WINDOW_EXITING in setup_vmcs_config() |
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On Wed, Jun 29, 2022, Vitaly Kuznetsov wrote: > CPU_BASED_{INTR,NMI}_WINDOW_EXITING controls are toggled dynamically by > vmx_enable_{irq,nmi}_window, handle_interrupt_window(), handle_nmi_window() > but setup_vmcs_config() doesn't check their existence. Add the check and > filter the controls out in vmx_exec_control(). > > No (real) functional change intended as all existing CPUs supporting > VMX are supposed to have these controls. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > arch/x86/kvm/vmx/vmx.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index da8bbba38d0e..89a3bbafa5af 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -2487,7 +2487,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf, > CPU_BASED_MWAIT_EXITING | > CPU_BASED_MONITOR_EXITING | > CPU_BASED_INVLPG_EXITING | > - CPU_BASED_RDPMC_EXITING; > + CPU_BASED_RDPMC_EXITING | > + CPU_BASED_INTR_WINDOW_EXITING | > + CPU_BASED_NMI_WINDOW_EXITING;
Requiring NMI_WINDOW_EXITING is wrong, KVM doesn't use NMI_WINDOW_EXITING if enable_vnmi == false:
if (!enable_vnmi || vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & GUEST_INTR_STATE_STI) { vmx_enable_irq_window(vcpu); return; }
exec_controls_setbit(to_vmx(vcpu), CPU_BASED_NMI_WINDOW_EXITING);
And enable_vnmi is cleared if PIN_BASED_VIRTUAL_NMIS are unsupported:
if (!cpu_has_virtual_nmis()) enable_vnmi = 0;
I suspect CPUs that don't support VIRTUAL_NMIS also don't support NMI_WINDOW_EXITING, and KVM explicitly supports such CPUs. See commit 8a1b43922d0d ("kvm: vmx: Reinstate support for CPUs without virtual NMI").
Making NMI_WINDOW_EXITING optional and then adding it to cpu_has_virtual_nmis() seems like the correct approach.
diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h index 069d8d298e1d..c34890e9fc2a 100644 --- a/arch/x86/kvm/vmx/capabilities.h +++ b/arch/x86/kvm/vmx/capabilities.h @@ -82,7 +82,8 @@ static inline bool cpu_has_vmx_basic_inout(void)
static inline bool cpu_has_virtual_nmis(void) { - return vmcs_config.pin_based_exec_ctrl & PIN_BASED_VIRTUAL_NMIS; + return vmcs_config.pin_based_exec_ctrl & PIN_BASED_VIRTUAL_NMIS && + vmcs_config.cpu_based_exec_ctrl & CPU_BASED_NMI_WINDOW_EXITING; }
static inline bool cpu_has_vmx_preemption_timer(void)
> opt = CPU_BASED_TPR_SHADOW | > CPU_BASED_USE_MSR_BITMAPS | > @@ -4300,6 +4302,10 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx) > { > u32 exec_control = vmcs_config.cpu_based_exec_ctrl; > > + /* INTR_WINDOW_EXITING and NMI_WINDOW_EXITING are toggled dynamically */ > + exec_control &= ~(CPU_BASED_INTR_WINDOW_EXITING | > + CPU_BASED_NMI_WINDOW_EXITING); > + > if (vmx->vcpu.arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT) > exec_control &= ~CPU_BASED_MOV_DR_EXITING; > > -- > 2.35.3 >
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