linux-kernel - Re: [PATCH linux-next 2/2] x86/xen/time: cleanup xen_tsc_safe

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Date:   Mon, 20 Feb 2023 23:01:18 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Krister Johansen <kjlx@...pleofstupid.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>, Jan Beulich <jbeulich@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Anthony Liguori <aliguori@...zon.com>,
        David Reaver <me@...idreaver.com>,
        Brendan Gregg <brendan@...el.com>
Subject: Re: [PATCH linux-next 2/2] x86/xen/time: cleanup
 xen_tsc_safe_clocksource

On Mon, Feb 20 2023 at 09:17, Krister Johansen wrote:
> @@ -495,8 +496,7 @@ static int __init xen_tsc_safe_clocksource(void)
>  	/* Leaf 4, sub-leaf 0 (0x40000x03) */
>  	cpuid_count(xen_cpuid_base() + 3, 0, &eax, &ebx, &ecx, &edx);
>  
> -	/* tsc_mode = no_emulate (2) */
> -	if (ebx != 2)
> +	if (ebx != XEN_CPUID_TSC_MODE_NEVER_EMULATE)
>  		return 0;
>  
>  	return 1;

What about removing more stupidity from that function?

static bool __init xen_tsc_safe_clocksource(void)
{
	u32 eax, ebx. ecx, edx;
 
	/* Leaf 4, sub-leaf 0 (0x40000x03) */
	cpuid_count(xen_cpuid_base() + 3, 0, &eax, &ebx, &ecx, &edx);

	return ebx == XEN_CPUID_TSC_MODE_NEVER_EMULATE;
}

Thanks,

        tglx