linux-kernel - Re: [PATCH] KVM: nVMX: expose INS/OUTS information support

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Date:   Mon, 5 Sep 2016 15:27:38 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jan Dakinevich <jan.dakinevich@...il.com>, kvm@...r.kernel.org
Cc:     rkrcmar@...hat.com, linux-kernel@...r.kernel.org,
        ynorov@...iumnetworks.com
Subject: Re: [PATCH] KVM: nVMX: expose INS/OUTS information support



On 04/09/2016 20:23, Jan Dakinevich wrote:
> Expose the feature to L1 hypervisor if host CPU supports it, since
> certain hypervisors requires it for own purposes.
> 
> According to Intel SDM A.1, if CPU supports the feature,
> VMX_INSTRUCTION_INFO field of VMCS will contain detailed information
> about INS/OUTS instructions handling. This field is already copied to
> VMCS12 for L1 hypervisor (see prepare_vmcs12 routine) independently
> feature presence.
> 
> Signed-off-by: Jan Dakinevich <jan.dakinevich@...il.com>
> ---
>  arch/x86/kvm/vmx.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index a4bb2bd..4fd22a6 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -939,6 +939,7 @@ static DEFINE_SPINLOCK(vmx_vpid_lock);
>  static struct vmcs_config {
>  	int size;
>  	int order;
> +	u32 basic_cap;
>  	u32 revision_id;
>  	u32 pin_based_exec_ctrl;
>  	u32 cpu_based_exec_ctrl;
> @@ -1215,6 +1216,11 @@ static inline bool cpu_has_vmx_ple(void)
>  		SECONDARY_EXEC_PAUSE_LOOP_EXITING;
>  }
>  
> +static inline bool cpu_has_vmx_basic_inout(void)
> +{
> +	return	(((u64)vmcs_config.basic_cap << 32) & VMX_BASIC_INOUT);
> +}
> +
>  static inline bool cpu_need_virtualize_apic_accesses(struct kvm_vcpu *vcpu)
>  {
>  	return flexpriority_enabled && lapic_in_kernel(vcpu);
> @@ -2877,6 +2883,8 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
>  		*pdata = VMCS12_REVISION | VMX_BASIC_TRUE_CTLS |
>  			   ((u64)VMCS12_SIZE << VMX_BASIC_VMCS_SIZE_SHIFT) |
>  			   (VMX_BASIC_MEM_TYPE_WB << VMX_BASIC_MEM_TYPE_SHIFT);
> +		if (cpu_has_vmx_basic_inout())
> +			*pdata |= VMX_BASIC_INOUT;
>  		break;
>  	case MSR_IA32_VMX_TRUE_PINBASED_CTLS:
>  	case MSR_IA32_VMX_PINBASED_CTLS:
> @@ -3458,6 +3466,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
>  
>  	vmcs_conf->size = vmx_msr_high & 0x1fff;
>  	vmcs_conf->order = get_order(vmcs_config.size);
> +	vmcs_conf->basic_cap = vmx_msr_high;

Bits 32-44 are already stored in vmcs_conf->size, so please make this
"vmx_msr_high & ~0x1fff".

Otherwise looks fine!

Paolo

>  	vmcs_conf->revision_id = vmx_msr_low;
>  
>  	vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
>