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

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Message-ID: <20181002092731.GB122128@gmail.com>
Date:   Tue, 2 Oct 2018 11:27:31 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: Re: [Patch v2 3/4] x86/speculation: Extend per process STIBP to AMD
 cpus.


* Tim Chen <tim.c.chen@...ux.intel.com> wrote:

> From: Thomas Lendacky <Thomas.Lendacky@....com>
> 
> 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@....com>
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> ---
>  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