linux-kernel - Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD systems

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Date:   Mon, 22 May 2017 18:21:43 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Yazen Ghannam <Yazen.Ghannam@....com>
Cc:     linux-pm@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        len.brown@...el.com, pavel@....cz
Subject: Re: [PATCH] x86/ACPI/cstate: Allow ACPI C1 FFH MWAIT use on AMD
 systems

On Wed, May 17, 2017 at 09:20:19AM -0500, Yazen Ghannam wrote:
> From: Yazen Ghannam <yazen.ghannam@....com>
> 
> AMD systems support the Monitor/Mwait instructions and these can be used
> for ACPI C1 in the same way as on Intel systems, with appropriate BIOS
> support.
> 
> Allow ffh_cstate_init() to succeed on AMD systems and make the Cstate
> description vendor-agnostic.
> 
> Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> ---
>  arch/x86/kernel/acpi/cstate.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
> index 8a908ae..4c5dd5d 100644
> --- a/arch/x86/kernel/acpi/cstate.c
> +++ b/arch/x86/kernel/acpi/cstate.c
> @@ -109,7 +109,7 @@ static long acpi_processor_ffh_cstate_probe_cpu(void *_cx)
>  			cx->type);
>  	}
>  	snprintf(cx->desc,
> -			ACPI_CX_DESC_LEN, "ACPI FFH INTEL MWAIT 0x%x",
> +			ACPI_CX_DESC_LEN, "ACPI FFH X86 MWAIT 0x%x",
>  			cx->address);
>  out:
>  	return retval;
> @@ -169,7 +169,8 @@ static int __init ffh_cstate_init(void)
>  {
>  	struct cpuinfo_x86 *c = &boot_cpu_data;
>  
> -	if (c->x86_vendor != X86_VENDOR_INTEL)
> +	if (c->x86_vendor != X86_VENDOR_INTEL &&
> +	    c->x86_vendor != X86_VENDOR_AMD)
>  		return -1;
>  
>  	cpu_cstate_entry = alloc_percpu(struct cstate_entry);

What about x86_idle?

That whole select_idle_routine() jumping through hoops. That's still
doing default_idle() on Zen, AFAICT.

Or am I missing something?

Because that still asks prefer_mwait_c1_over_halt() and that needs a
family check or whatever...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--