linux-kernel - Re: [PATCH 1/2] x86/bugs: Update when to check for the LS

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Date:   Tue, 3 Jul 2018 10:12:03 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bpetkov@...e.de>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH 1/2] x86/bugs: Update when to check for the LS_CFG SSBD
 mitigation

On Mon, Jul 02, 2018 at 04:35:53PM -0500, Tom Lendacky wrote:
> If either the X86_FEATURE_AMD_SSBD or X86_FEATURE_VIRT_SSBD features are
> present, then there is no need to perform the check for the LS_CFG SSBD
> mitigation support.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

> ---
>  arch/x86/kernel/cpu/amd.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 082d787..38915fb 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -543,7 +543,9 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
>  		nodes_per_socket = ((value >> 3) & 7) + 1;
>  	}
>  
> -	if (c->x86 >= 0x15 && c->x86 <= 0x17) {
> +	if (!boot_cpu_has(X86_FEATURE_AMD_SSBD) &&
> +	    !boot_cpu_has(X86_FEATURE_VIRT_SSBD) &&
> +	    c->x86 >= 0x15 && c->x86 <= 0x17) {
>  		unsigned int bit;
>  
>  		switch (c->x86) {
>