linux-kernel - Re: [PATCH 00/11] Add support for Hygon's Dhyana Family 18h processor

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Date:   Wed, 13 Jun 2018 22:51:29 +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, peterz@...radead.org,
        tony.luck@...el.com, pbonzini@...hat.com, rkrcmar@...hat.com,
        boris.ostrovsky@...cle.com, jgross@...e.com, rjw@...ysocki.net,
        lenb@...nel.org, viresh.kumar@...aro.org, mchehab@...nel.org,
        trenn@...e.com, shuah@...nel.org, zhangpanyong@...on.cn,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-x86_64@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-pm@...r.kernel.org, kvm@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH 00/11] Add support for Hygon's Dhyana Family 18h processor

On Sat, Jun 09, 2018 at 09:20:10PM +0800, Pu Wen wrote:
> As a new x86 CPU Vendor, Chengdu Haiguang IC Design Co., Ltd (Hygon)
> is a Joint Venture between AMD and Haiguang Information Technology Co.,
> Ltd., and aims at providing high performance x86 processor for China
> server market.
> 
> The first generation Hygon's processor(Dhyana) originates from AMD
> technology and shares most of the architecture with AMD's family 17h,
> but with different CPU Vendor ID("HygonGenuine")/PCIE Device Vendor ID
> (0x1D94)/Family series number(Family 18h).
> 
> To enable the support of Linux kernel to Hygon's CPU, we added a new
> vendor type (X86_VENDOR_HYGON, with value of 9) in arch/x86/include/
> asm/processor.h, and shared most of kernel support codes with AMD
> family 17h.
> 
> These patches have been applied and tested successfully in Hygon's
> Dhyana SoC silicon. Also tested on AMD's EPYC (Family 17h) processor
> works fine and makes no harm to existing codes.

Well, I don't like this diffstat:

 37 files changed, 183 insertions(+), 56 deletions(-)

which adds a lot of code checking this new vendor. But then it adds in
the AMD paths and I don't see it being any different from an AMD CPU. So
it does the same a Zen does but then it is Hygon.

So I'd prefer to *not* sprinkle those X86_VENDOR_HYGON checks everywhere
but simply have the vendor be X86_VENDOR_AMD and only the user-visible
reporting to show that it is Hygon. Because to the kernel it is an AMD
CPU - only the superficial attributes are something else. Oh well, and
PCI device IDs but that's like another CPU revision.

Thx.

-- 
Regards/Gruss,
    Boris.

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