Re: [Xen-devel] [PATCH] xen: Filter out MSR write events

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Apr 11, 2016 at 07:41:54PM +0300, Razvan Cojocaru wrote:
> This patch only allows introspection-related MSR write events to
> be sent out, improving performance. Should additional events be
> required, they can then simply be added to the list of
> vmx_introspection_force_enabled_msrs[].
> 
> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

Thought should there be some .. dynamic mechanism to update
the MSR list? Or remove entries (or temporarily blacklist
the built-one ins), etc?

> ---
>  xen/arch/x86/hvm/hvm.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index f24126d..21ba611 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -3688,6 +3688,17 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t 
> *msr_content)
>      goto out;
>  }
>  
> +static bool_t is_introspection_msr(unsigned int msr)
> +{
> +    unsigned int i;
> +
> +    for ( i = 0; i < vmx_introspection_force_enabled_msrs_size; i++ )
> +        if ( msr == vmx_introspection_force_enabled_msrs[i] )
> +            return 1;
> +
> +    return 0;
> +}
> +
>  int hvm_msr_write_intercept(unsigned int msr, uint64_t msr_content,
>                              bool_t may_defer)
>  {
> @@ -3703,7 +3714,8 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t 
> msr_content,
>      hvm_cpuid(1, NULL, NULL, NULL, &edx);
>      mtrr = !!(edx & cpufeat_mask(X86_FEATURE_MTRR));
>  
> -    if ( may_defer && unlikely(currad->monitor.mov_to_msr_enabled) )
> +    if ( may_defer && unlikely(currad->monitor.mov_to_msr_enabled) &&
> +         is_introspection_msr(msr) )
>      {
>          ASSERT(v->arch.vm_event);
>  
> -- 
> 2.8.0
> 
> 
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