Re: [PATCH v2 1/7] x86/hyper-v: check for required priviliges in hyperv_init()

[Thomas Gleixner]

On Wed, 13 Dec 2017, Vitaly Kuznetsov wrote:

> In hyperv_init() we presume we always have access to VP index and hypercall
> MSRs while according to the specification we should check if we're allowed
> to access the corresponding MSRs before accessing them.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

> ---
>  arch/x86/hyperv/hv_init.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 189a398290db..21f9d53d9f00 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -110,12 +110,19 @@ static int hv_cpu_init(unsigned int cpu)
>   */
>  void hyperv_init(void)
>  {
> -	u64 guest_id;
> +	u64 guest_id, required_msrs;
>  	union hv_x64_msr_hypercall_contents hypercall_msr;
>  
>  	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
>  		return;
>  
> +	/* Absolutely required MSRs */
> +	required_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE |
> +		HV_X64_MSR_VP_INDEX_AVAILABLE;
> +
> +	if ((ms_hyperv.features & required_msrs) != required_msrs)
> +		return;
> +
>  	/* Allocate percpu VP index */
>  	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
>  				    GFP_KERNEL);
> -- 
> 2.14.3
> 
>