Re: [PATCH 4/4] KVM: VMX: Add instruction rdtscp support for guest

[Avi Kivity <avi@redhat.com>]

On 12/16/2009 07:48 AM, Sheng Yang wrote:
> Before enabling, execution of "rdtscp" in guest would result in #UD.
>
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 4f865e8..3a84acf 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -532,6 +532,7 @@ struct kvm_x86_ops {
>   	int (*get_tdp_level)(void);
>   	u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
>   	bool (*gb_page_enable)(void);
> +	bool (*rdtscp_enable)(void);
>    

Naming - a better name is rdtsp_supported().  rdtscp_enable sounds like 
you change it from disabled to enabled.

> @@ -913,6 +924,9 @@ static void setup_msrs(struct vcpu_vmx *vmx)
>   		index = __find_msr_index(vmx, MSR_CSTAR);
>   		if (index>= 0)
>   			move_msr_up(vmx, index, save_nmsrs++);
> +		index = __find_msr_index(vmx, MSR_TSC_AUX);
> +		if (index>= 0)
> +			move_msr_up(vmx, index, save_nmsrs++);
>    

Only if rdtscp is enabled in the guest's cpuid, so we don't play with 
this unnecessarily.  If it isn't, we should trap rdtscp and inject #UD.  
If it is, support the msr and don't trap.

>   		/*
>   		 * MSR_K6_STAR is only needed on long mode guests, and only
>   		 * if efer.sce is enabled.
> @@ -1002,6 +1016,10 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
>   	case MSR_IA32_SYSENTER_ESP:
>   		data = vmcs_readl(GUEST_SYSENTER_ESP);
>   		break;
> +	case MSR_TSC_AUX:
> +		if (!vmx_rdtscp_enable())
> +			return 1;
>    

Again, check the guest rdtscp bit, not (just) the host's.


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