Re: [Patch v2 2/4] x86/speculation: Provide application property based STIBP protection

[Tim Chen]

On 10/02/2018 12:10 PM, Thomas Gleixner wrote:
> On Tue, 25 Sep 2018, Tim Chen wrote:
> 
>> This patch provides an application property based spectre_v2
> 
> # git grep 'This patch' Documentation/process/
> 
>> protection with STIBP against attack from another app from
> 
> s/app/application/ please. This is not android.
> 
>> a sibling hyper-thread.  For security sensitive non-dumpable
>> app, STIBP will be turned on before switching to it for Intel
>> processors vulnerable to spectre_v2.
> 
> What has this to do with Intel processors?
> 
>> -static __always_inline void intel_set_ssb_state(unsigned long tifn)
>> +static __always_inline void set_spec_ctrl_state(unsigned long tifn)
>>  {
>> -	u64 msr = x86_spec_ctrl_base | ssbd_tif_to_spec_ctrl(tifn);
>> +	u64 msr = x86_spec_ctrl_base;
>> +
>> +	if (static_cpu_has(X86_FEATURE_SSBD))
>> +		msr |= ssbd_tif_to_spec_ctrl(tifn);
>> +
>> +	if (cpu_smt_control == CPU_SMT_ENABLED)
>> +		msr |= stibp_tif_to_spec_ctrl(tifn);
> 
> Oh no. We are not adding yet another conditional into switch to. Either
> that's done unconditionally or this wants to have a static key.

Okay, will add a static_key to indicate that SMT is in use.

Tim

> 
>>  	wrmsrl(MSR_IA32_SPEC_CTRL, msr);
> 
> Thanks,
> 
> 	tglx
>