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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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?

~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);
>  
>      /*


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