Re: [PATCH 9/9] Allow setting the SVME bit v5

[Avi Kivity <avi@redhat.com>]

Joerg Roedel wrote:
> On Mon, Oct 20, 2008 at 07:04:50PM +0200, Alexander Graf wrote:
>   
>> Normally setting the SVME bit in EFER is not allowed, as we did
>> not support SVM. Not since we do, we should also allow enabling
>> SVM mode.
>>
>> v2 comes as last patch, so we don't enable half-ready code
>> v4 introduces a module option to enable SVM
>>
>> Signed-off-by: Alexander Graf <agraf@suse.de>
>> ---
>>  arch/x86/kvm/svm.c |    6 ++++++
>>  1 files changed, 6 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index 4582699..1e63860 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -68,6 +68,9 @@ static int npt = 1;
>>  
>>  module_param(npt, int, S_IRUGO);
>>  
>> +static int nested = 0;
>> +module_param(nested, int, S_IRUGO);
>> +
>>  static void kvm_reput_irq(struct vcpu_svm *svm);
>>  static void svm_flush_tlb(struct kvm_vcpu *vcpu);
>>  
>> @@ -457,6 +460,9 @@ static __init int svm_hardware_setup(void)
>>  	if (boot_cpu_has(X86_FEATURE_NX))
>>  		kvm_enable_efer_bits(EFER_NX);
>>  
>> +	if (nested)
>> +		kvm_enable_efer_bits(MSR_EFER_SVME_MASK);
>> +
>>  	for_each_online_cpu(cpu) {
>>  		r = svm_cpu_init(cpu);
>>  		if (r)
>>     
>
>
> What I think is missing here is some kind of userspace interface. If we
> do it this way (with a kernel parameter) we should expose to userspace
> if nested svm is enabled. This way userspace knows whether it has to set
> the SVM CPUID bit or not.
>   

Right.  There's the KVM_GET_SUPPORTED_CPUID thing that can be used for this.

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