Re: [PATCH] KVM: nVMX: Add preemption timer support

[Gleb Natapov <gleb@redhat.com>]

On Wed, Mar 13, 2013 at 11:31:24AM +0100, Jan Kiszka wrote:
> Provided the host has this feature, it's straightforward to offer it to
> the guest as well. We just need to load to timer value on L2 entry if
> the feature was enabled by L1 and watch out for the corresponding exit
> reason.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  arch/x86/include/asm/vmx.h      |    3 +++
>  arch/x86/include/uapi/asm/vmx.h |    5 +++--
>  arch/x86/kvm/vmx.c              |   17 ++++++++++++++---
>  3 files changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index 056bda5..fc1c313 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -70,6 +70,7 @@
>  #define PIN_BASED_EXT_INTR_MASK                 0x00000001
>  #define PIN_BASED_NMI_EXITING                   0x00000008
>  #define PIN_BASED_VIRTUAL_NMIS                  0x00000020
> +#define PIN_BASED_VMX_PREEMPTION_TIMER          0x00000040
>  
>  #define PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR	0x00000016
>  
> @@ -95,6 +96,7 @@
>  
>  #define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR	0x000011ff
>  
> +#define VMX_MISC_PREEMPTION_TIMER_RATE_MASK	0x0000001f
>  #define VMX_MISC_SAVE_EFER_LMA			0x00000020
What is this patch against? I do not see VMX_MISC_SAVE_EFER_LMA in
kvm.git queue.

>  
>  /* VMCS Encodings */
> @@ -217,6 +219,7 @@ enum vmcs_field {
>  	GUEST_INTERRUPTIBILITY_INFO     = 0x00004824,
>  	GUEST_ACTIVITY_STATE            = 0X00004826,
>  	GUEST_SYSENTER_CS               = 0x0000482A,
> +	VMX_PREEMPTION_TIMER_VALUE      = 0x0000482E,
>  	HOST_IA32_SYSENTER_CS           = 0x00004c00,
>  	CR0_GUEST_HOST_MASK             = 0x00006000,
>  	CR4_GUEST_HOST_MASK             = 0x00006002,
> diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
> index 2871fcc..d651082 100644
> --- a/arch/x86/include/uapi/asm/vmx.h
> +++ b/arch/x86/include/uapi/asm/vmx.h
> @@ -65,6 +65,7 @@
>  #define EXIT_REASON_EOI_INDUCED         45
>  #define EXIT_REASON_EPT_VIOLATION       48
>  #define EXIT_REASON_EPT_MISCONFIG       49
> +#define EXIT_REASON_PREEMPTION_TIMER    52
>  #define EXIT_REASON_WBINVD              54
>  #define EXIT_REASON_XSETBV              55
>  #define EXIT_REASON_APIC_WRITE          56
> @@ -110,7 +111,7 @@
>  	{ EXIT_REASON_EOI_INDUCED,           "EOI_INDUCED" }, \
>  	{ EXIT_REASON_INVALID_STATE,         "INVALID_STATE" }, \
>  	{ EXIT_REASON_INVD,                  "INVD" }, \
> -	{ EXIT_REASON_INVPCID,               "INVPCID" }
> -
> +	{ EXIT_REASON_INVPCID,               "INVPCID" }, \
> +	{ EXIT_REASON_PREEMPTION_TIMER,      "PREEMPTION_TIMER" }
>  
>  #endif /* _UAPIVMX_H */
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 0f0cc6a..5b8eeb6 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -298,7 +298,8 @@ struct __packed vmcs12 {
>  	u32 guest_activity_state;
>  	u32 guest_sysenter_cs;
>  	u32 host_ia32_sysenter_cs;
> -	u32 padding32[8]; /* room for future expansion */
> +	u32 vmx_preemption_timer_value;
> +	u32 padding32[7]; /* room for future expansion */
>  	u16 virtual_processor_id;
>  	u16 guest_es_selector;
>  	u16 guest_cs_selector;
> @@ -537,6 +538,7 @@ static const unsigned short vmcs_field_to_offset_table[] = {
>  	FIELD(GUEST_ACTIVITY_STATE, guest_activity_state),
>  	FIELD(GUEST_SYSENTER_CS, guest_sysenter_cs),
>  	FIELD(HOST_IA32_SYSENTER_CS, host_ia32_sysenter_cs),
> +	FIELD(VMX_PREEMPTION_TIMER_VALUE, vmx_preemption_timer_value),
>  	FIELD(CR0_GUEST_HOST_MASK, cr0_guest_host_mask),
>  	FIELD(CR4_GUEST_HOST_MASK, cr4_guest_host_mask),
>  	FIELD(CR0_READ_SHADOW, cr0_read_shadow),
> @@ -2049,7 +2051,8 @@ static __init void nested_vmx_setup_ctls_msrs(void)
>  	 */
>  	nested_vmx_pinbased_ctls_low |= PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
>  	nested_vmx_pinbased_ctls_high &= PIN_BASED_EXT_INTR_MASK |
> -		PIN_BASED_NMI_EXITING | PIN_BASED_VIRTUAL_NMIS;
> +		PIN_BASED_NMI_EXITING | PIN_BASED_VIRTUAL_NMIS |
> +		PIN_BASED_VMX_PREEMPTION_TIMER;
>  	nested_vmx_pinbased_ctls_high |= PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
>  
>  	/*
> @@ -2110,7 +2113,8 @@ static __init void nested_vmx_setup_ctls_msrs(void)
>  
>  	/* miscellaneous data */
>  	rdmsr(MSR_IA32_VMX_MISC, nested_vmx_misc_low, nested_vmx_misc_high);
> -	nested_vmx_misc_low &= VMX_MISC_SAVE_EFER_LMA;
> +	nested_vmx_misc_low &= VMX_MISC_PREEMPTION_TIMER_RATE_MASK |
> +		VMX_MISC_SAVE_EFER_LMA;
>  	nested_vmx_misc_high = 0;
>  }
>  
> @@ -6191,6 +6195,9 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
>  	case EXIT_REASON_EPT_VIOLATION:
>  	case EXIT_REASON_EPT_MISCONFIG:
>  		return 0;
> +	case EXIT_REASON_PREEMPTION_TIMER:
> +		return vmcs12->pin_based_vm_exec_control &
> +			PIN_BASED_VMX_PREEMPTION_TIMER;
>  	case EXIT_REASON_WBINVD:
>  		return nested_cpu_has2(vmcs12, SECONDARY_EXEC_WBINVD_EXITING);
>  	case EXIT_REASON_XSETBV:
> @@ -6984,6 +6991,10 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  		(vmcs_config.pin_based_exec_ctrl |
>  		 vmcs12->pin_based_vm_exec_control));
>  
> +	if (vmcs12->pin_based_vm_exec_control & PIN_BASED_VMX_PREEMPTION_TIMER)
> +		vmcs_write32(VMX_PREEMPTION_TIMER_VALUE,
> +			     vmcs12->vmx_preemption_timer_value);
> +
>  	/*
>  	 * Whether page-faults are trapped is determined by a combination of
>  	 * 3 settings: PFEC_MASK, PFEC_MATCH and EXCEPTION_BITMAP.PF.
> -- 
> 1.7.3.4

--
			Gleb.