Re: [Patch v2 3/4] x86/speculation: Extend per process STIBP to AMD cpus.

[Ingo Molnar]

* Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> wrote:

> From: Thomas Lendacky <Thomas.Lendacky@xxxxxxx>
> 
> We extend the app to app spectre v2 mitigation using STIBP
> to the AMD cpus. We need to take care of special

s/to the AMD cpus
 /to AMD CPUs

> cases for AMD cpu's update of SPEC_CTRL MSR to avoid double
> writing of MSRs from update to SSBD and STIBP.

s/AMD cpu
 /AMD CPU

> 
> Originally-by: Thomas Lendacky <Thomas.Lendacky@xxxxxxx>
> Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/kernel/process.c | 48 +++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 38 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index cb24014..4a3a672 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -399,6 +399,10 @@ static __always_inline void set_spec_ctrl_state(unsigned long tifn)
>  {
>  	u64 msr = x86_spec_ctrl_base;
>  
> +	/*
> +	 * AMD cpu may have used a different method to update SSBD, so
> +	 * we need to be sure we are using the SPEC_CTRL MSR for SSBD.

s/AMD cpu may have used a different method to update SSBD
 /AMD CPUs may use a different method to update the SSBD

Thanks,

	Ingo