Re: [PATCH] KVM: nVMX: Add support for activity state HLT

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2013-12-05 10:52, Paolo Bonzini wrote:
> Il 04/12/2013 08:58, Jan Kiszka ha scritto:
>> We can easily emulate the HLT activity state for L1: If it decides that
>> L2 shall be halted on entry, just invoke the normal emulation of halt
>> after switching to L2. We do not depend on specific host features to
>> provide this, so we can expose the capability unconditionally.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>
>> Jailhouse would like to use this. Experimental code works fine so far,
>> both on patched KVM and real HW.
> 
> Nice. :)
> 
> Do you have a testcase for kvm-unit-tests?

Not yet. Maybe I will find a little time these days.

Jan

> 
> Paolo
> 
>>  arch/x86/include/asm/vmx.h | 1 +
>>  arch/x86/kvm/vmx.c         | 7 ++++++-
>>  2 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
>> index 966502d..2067264 100644
>> --- a/arch/x86/include/asm/vmx.h
>> +++ b/arch/x86/include/asm/vmx.h
>> @@ -100,6 +100,7 @@
>>  
>>  #define VMX_MISC_PREEMPTION_TIMER_RATE_MASK	0x0000001f
>>  #define VMX_MISC_SAVE_EFER_LMA			0x00000020
>> +#define VMX_MISC_ACTIVITY_HLT			0x00000040
>>  
>>  /* VMCS Encodings */
>>  enum vmcs_field {
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index b2fe1c2..00faf1f 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -2279,6 +2279,7 @@ static __init void nested_vmx_setup_ctls_msrs(void)
>>  	rdmsr(MSR_IA32_VMX_MISC, nested_vmx_misc_low, nested_vmx_misc_high);
>>  	nested_vmx_misc_low &= VMX_MISC_PREEMPTION_TIMER_RATE_MASK |
>>  		VMX_MISC_SAVE_EFER_LMA;
>> +	nested_vmx_misc_low |= VMX_MISC_ACTIVITY_HLT;
>>  	nested_vmx_misc_high = 0;
>>  }
>>  
>> @@ -7882,7 +7883,8 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>>  		return 1;
>>  	}
>>  
>> -	if (vmcs12->guest_activity_state != GUEST_ACTIVITY_ACTIVE) {
>> +	if (vmcs12->guest_activity_state != GUEST_ACTIVITY_ACTIVE &&
>> +	    vmcs12->guest_activity_state != GUEST_ACTIVITY_HLT) {
>>  		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
>>  		return 1;
>>  	}
>> @@ -8011,6 +8013,9 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>>  
>>  	prepare_vmcs02(vcpu, vmcs12);
>>  
>> +	if (vmcs12->guest_activity_state == GUEST_ACTIVITY_HLT)
>> +		return kvm_emulate_halt(vcpu);
>> +
>>  	/*
>>  	 * Note no nested_vmx_succeed or nested_vmx_fail here. At this point
>>  	 * we are no longer running L1, and VMLAUNCH/VMRESUME has not yet
>>
> 

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