Re: [PATCH] KVM: nVMX: Provide EFER.LMA saving support

[Paolo Bonzini <pbonzini@redhat.com>]

Il 13/03/2013 16:06, Jan Kiszka ha scritto:
> We will need EFER.LMA saving to provide unrestricted guest mode. All
> what is missing for this is picking up EFER.LMA from VM_ENTRY_CONTROLS
> on L2->L1 switches. If the host does not support EFER.LMA saving,
> no change is performed, otherwise we properly emulate for L1 what the
> hardware does for L0. Advertise the support, depending on the host
> feature.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
> 
> It's not yet very helpful for upstream - due to lacking nEPT, but it is
> also minimal invasive and helps cleaning my queue. Finally some bits
> are needed also for the preemption timer support posted earlier today.
> 
>  arch/x86/include/asm/vmx.h |    2 ++
>  arch/x86/kvm/vmx.c         |   13 ++++++++++++-
>  2 files changed, 14 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index 5fb6e24..e1cc048c 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -93,6 +93,8 @@
>  
>  #define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR	0x000011ff
>  
> +#define VMX_MISC_SAVE_EFER_LMA			0x00000020
> +
>  /* VMCS Encodings */
>  enum vmcs_field {
>  	VIRTUAL_PROCESSOR_ID            = 0x00000000,
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index b73989d..d4a747f 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2022,6 +2022,7 @@ static u32 nested_vmx_secondary_ctls_low, nested_vmx_secondary_ctls_high;
>  static u32 nested_vmx_pinbased_ctls_low, nested_vmx_pinbased_ctls_high;
>  static u32 nested_vmx_exit_ctls_low, nested_vmx_exit_ctls_high;
>  static u32 nested_vmx_entry_ctls_low, nested_vmx_entry_ctls_high;
> +static u32 nested_vmx_misc_low, nested_vmx_misc_high;
>  static __init void nested_vmx_setup_ctls_msrs(void)
>  {
>  	/*
> @@ -2104,6 +2105,11 @@ static __init void nested_vmx_setup_ctls_msrs(void)
>  	nested_vmx_secondary_ctls_high &=
>  		SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
>  		SECONDARY_EXEC_WBINVD_EXITING;
> +
> +	/* 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_high = 0;
>  }
>  
>  static inline bool vmx_control_verify(u32 control, u32 low, u32 high)
> @@ -2174,7 +2180,8 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
>  					nested_vmx_entry_ctls_high);
>  		break;
>  	case MSR_IA32_VMX_MISC:
> -		*pdata = 0;
> +		*pdata = vmx_control_msr(nested_vmx_misc_low,
> +					 nested_vmx_misc_high);
>  		break;
>  	/*
>  	 * These MSRs specify bits which the guest must keep fixed (on or off)
> @@ -7397,6 +7404,10 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  	vmcs12->guest_pending_dbg_exceptions =
>  		vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS);
>  
> +	vmcs12->vm_entry_controls =
> +		(vmcs12->vm_entry_controls & ~VM_ENTRY_IA32E_MODE) |
> +		(vmcs_read32(VM_ENTRY_CONTROLS) & VM_ENTRY_IA32E_MODE);
> +
>  	/* TODO: These cannot have changed unless we have MSR bitmaps and
>  	 * the relevant bit asks not to trap the change */
>  	vmcs12->guest_ia32_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>