linux-kernel - Re: [PATCH v5 08/16] x86/apic: add modern APIC support for Hygon

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Message-ID: <20180904183301.GN32615@zn.tnic>
Date:   Tue, 4 Sep 2018 20:33:01 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Pu Wen <puwen@...on.cn>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, thomas.lendacky@....com, pbonzini@...hat.com,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH v5 08/16] x86/apic: add modern APIC support for Hygon

On Wed, Aug 29, 2018 at 08:44:30PM +0800, Pu Wen wrote:
> Hygon processors use modern APIC, so just return in modern_apic() and
> sync_Arb_IDs(). And should break in switch case in detect_init_API().
> 
> When running on 32 bit mode, should set bigsmp if there are more than
> 8 cores.
> 
> Signed-off-by: Pu Wen <puwen@...on.cn>
> ---
>  arch/x86/kernel/apic/apic.c     | 19 ++++++++++++++-----
>  arch/x86/kernel/apic/probe_32.c |  1 +
>  2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index 84132ed..a62968e 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -220,10 +220,15 @@ static inline int lapic_is_integrated(void)
>   */
>  static int modern_apic(void)
>  {
> -	/* AMD systems use old APIC versions, so check the CPU */
> -	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
> -	    boot_cpu_data.x86 >= 0xf)
> +	/*
> +	 * Old AMD systems use old APIC versions, newer AMD systems
> +	 * and Hygon systems use modern APIC, so check the CPU
> +	 */
> +	if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
> +	     boot_cpu_data.x86 >= 0xf) ||
> +	     boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
>  		return 1;

Those compound conditionals are not nice to read. Just add yours
underneath:

	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
	    boot_cpu_data.x86 >= 0xf)
		return 1;

	if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
		return 1;

Do that where applicable and where it makes sense, syntax-wise to have a
separate vendor == HYGON check in the other patches too.

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.