linux-kernel - Re: [PATCH v5 03/16] x86/mtrr: get MTRR number and support TOP

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Date:   Mon, 3 Sep 2018 21:04:38 +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 03/16] x86/mtrr: get MTRR number and support TOP_MEM2

On Wed, Aug 29, 2018 at 08:43:23PM +0800, Pu Wen wrote:
> Hygon CPU have a special magic MSR way to force WB for memory >4GB,

It was "Hygon Dhyana" before now "Hygon" only. Can we agree on the
naming nomenclature and stick with it.

Also, it is "The ... CPU has a special..."

> and also support TOP_MEM2. Therefore, it is necessary to add Hygon
> support in amd_special_default_mtrr().
> 
> The MtrrFixDramModEn bit on Hygon platform should also be set to 1
> during BIOS initialization of the fixed MTRRs, then cleared to 0 for
> operation.
> 
> The number of variable MTRRs for Hygon is 2 as AMD's.
> 
> Signed-off-by: Pu Wen <puwen@...on.cn>
> ---
>  arch/x86/kernel/cpu/mtrr/cleanup.c | 3 ++-
>  arch/x86/kernel/cpu/mtrr/generic.c | 5 +++--
>  arch/x86/kernel/cpu/mtrr/mtrr.c    | 2 +-
>  3 files changed, 6 insertions(+), 4 deletions(-)

...

> diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
> index e12ee86..77c3eaa 100644
> --- a/arch/x86/kernel/cpu/mtrr/generic.c
> +++ b/arch/x86/kernel/cpu/mtrr/generic.c
> @@ -49,8 +49,9 @@ static inline void k8_check_syscfg_dram_mod_en(void)
>  {
>  	u32 lo, hi;
>  
> -	if (!((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) &&
> -	      (boot_cpu_data.x86 >= 0x0f)))
> +	if (!((boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
> +	       boot_cpu_data.x86 >= 0x0f) ||
> +	       boot_cpu_data.x86_vendor == X86_VENDOR_HYGON))

Why are you even touching this statement? The function returns early on
!X86_VENDOR_AMD.

-- 
Regards/Gruss,
    Boris.

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