Re: [Xen-devel] [PATCH v2 1/3] Nested VMX: Check VMX capability before read VMX related MSRs.

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Andrew Cooper wrote on 2013-09-10:
> On 10/09/13 07:14, Yang Zhang wrote:
>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>> 
>> VMX MSRs only available when the CPU support the VMX feature. In
>> addition,
>> VMX_TRUE* MSRs only available when bit 55 of VMX_BASIC MSR is set.
>> 
>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>> ---
>>  xen/arch/x86/hvm/vmx/vvmx.c |   19 +++++++++++++++++++
>>  1 files changed, 19 insertions(+), 0 deletions(-)
>> diff --git a/xen/arch/x86/hvm/vmx/vvmx.c
>> b/xen/arch/x86/hvm/vmx/vvmx.c index cecc72f..c6c8b88 100644
>> --- a/xen/arch/x86/hvm/vmx/vvmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
>> @@ -1814,12 +1814,31 @@ int nvmx_handle_invvpid(struct cpu_user_regs
>> *regs)  int nvmx_msr_read_intercept(unsigned int msr, u64
>> *msr_content)  {
>>      struct vcpu *v = current; +    unsigned int eax, ebx, ecx, edx;
>>      u64 data = 0, host_data = 0; int r = 1;
>>      
>>      if ( !nestedhvm_enabled(v->domain) )
>>          return 0;
>> +    /*
>> +     * VMX capablitys MSRs available only when guest
> 
> sp. capability.
> 
>> +     * support VMX.
>> +     */
>> +    hvm_cpuid(0x1, &eax, &ebx, &ecx, &edx);
>> +    if ( !(ecx & cpufeat_mask(X86_FEATURE_VMXE)) )
>> +        return 0;
>> +
>> +    /*
>> +     * Those MSRs available only when bit 55 of
>> +     * MSR_IA32_VMX_BASIC is set.
> 
> Given pedantry about spelling,
> 
> "Those MSRs are"
> 
> Furthermore, do those comments really not fit on a single line?
The first one is ok in a single line, but the second one will exceed the 80 
characters.

> 
> ~Andrew
> 
>> +     */
>> +    rdmsrl(MSR_IA32_VMX_BASIC, data);
>> +    if ( msr >= MSR_IA32_VMX_TRUE_PINBASED_CTLS &&
>> +         msr <= MSR_IA32_VMX_TRUE_ENTRY_CTLS &&
>> +         !(data & VMX_BASIC_DEFAULT1_ZERO) )
>> +        return 0;
>> +
>>      rdmsrl(msr, host_data);
>>      
>>      /*


Best regards,
Yang


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