Re: [PATCH] Support for GUEST_SMBASE vmcs field for nested virtualization

[Avi Kivity <avi@redhat.com>]

On 06/06/2012 02:37 PM, Matthias Lange wrote:
> Hi,
> 
> the following patch adds support for the GUEST_SMBASE field in the VMCS for
> the case of nested virtualization. There are hypervisors that try to access
> that mandatory field. The patch avoids returning a "unsupported vmcs field"
> error to the L1 hypervisor by adding the GUEST_SMBASE field into the vmcs12
> struct.
> 
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index 31f180c..6a14720 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -194,6 +194,7 @@ enum vmcs_field {
>  	GUEST_TR_AR_BYTES               = 0x00004822,
>  	GUEST_INTERRUPTIBILITY_INFO     = 0x00004824,
>  	GUEST_ACTIVITY_STATE            = 0X00004826,
> +	GUEST_SMBASE			= 0x00004828,
>  	GUEST_SYSENTER_CS               = 0x0000482A,
>  	HOST_IA32_SYSENTER_CS           = 0x00004c00,
>  	CR0_GUEST_HOST_MASK             = 0x00006000,
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 32eb588..88e21e9 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -294,7 +294,8 @@ struct __packed vmcs12 {
>  	u32 guest_activity_state;
>  	u32 guest_sysenter_cs;
>  	u32 host_ia32_sysenter_cs;
> -	u32 padding32[8]; /* room for future expansion */
> +	u32 guest_smbase;
> +	u32 padding32[7]; /* room for future expansion */
>  	u16 virtual_processor_id;
>  	u16 guest_es_selector;
>  	u16 guest_cs_selector;

This is okay now.

> @@ -6536,6 +6538,7 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  	vmcs_write32(GUEST_INTERRUPTIBILITY_INFO,
>  		vmcs12->guest_interruptibility_info);
>  	vmcs_write32(GUEST_ACTIVITY_STATE, vmcs12->guest_activity_state);
> +	vmcs_write32(GUEST_SMBASE, vmcs12->guest_smbase);
>  	vmcs_write32(GUEST_SYSENTER_CS, vmcs12->guest_sysenter_cs);
>  	vmcs_writel(GUEST_DR7, vmcs12->guest_dr7);
>  	vmcs_writel(GUEST_RFLAGS, vmcs12->guest_rflags);
> @@ -6937,6 +6940,7 @@ void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  	vmcs12->guest_idtr_base = vmcs_readl(GUEST_IDTR_BASE);
>  
>  	vmcs12->guest_activity_state = vmcs_read32(GUEST_ACTIVITY_STATE);
> +	vmcs12->guest_smbase = vmcs_read32(GUEST_SMBASE);
>  	vmcs12->guest_interruptibility_info =
>  		vmcs_read32(GUEST_INTERRUPTIBILITY_INFO);
>  	vmcs12->guest_pending_dbg_exceptions =


I missed this earlier: I don't think we need this.  If we do implement
SMM, anything touching SMBASE (SMI delivery and RSM) will be emulated,
so we don't need anything in vmcs02 (just vmcs12, which is handled by
the code above).

-- 
error compiling committee.c: too many arguments to function