linux-kernel - Re: [PATCH 2/4] x86/amd_nb: add support for newer PCI topologies

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Message-ID: <20181105233212.GC27399@amd.com>
Date:   Mon, 5 Nov 2018 23:32:16 +0000
From:   "Woods, Brian" <Brian.Woods@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "Woods, Brian" <Brian.Woods@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Clemens Ladisch <clemens@...isch.de>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>, Pu Wen <puwen@...on.cn>,
        Jia Zhang <qianyue.zj@...baba-inc.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 2/4] x86/amd_nb: add support for newer PCI topologies

On Mon, Nov 05, 2018 at 10:42:33PM +0100, Borislav Petkov wrote:
> Yes please. Because this is the usual kernel coding style of calling a
> function (or a loop which has some result in this case) and testing that
> result immediately after the function call.

Done.

> You say "correct" as there is a special one. But the text before it says
> they're "functionally the same" wrt DF/SMN access so it sounds to me
> like we wanna map the first one we find and ignore the others.
> 
> I.e., we wanna say
> 
> "... so the DF/SMN interfaces get mapped to the *first* PCI root and the
> others N-1 ignored."
> 
> Or am I misreading this?
> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Good mailing practices for 400: avoid top-posting and trim the reply.

Your understanding is correct.  It's more so that the following DF/SMN
interface gets mapped correctly.
		/*
		 * If there are more PCI root devices than data fabric/
		 * system management network interfaces, then the (N)
		 * PCI roots per DF/SMN interface are functionally the
		 * same (for DF/SMN access) and N-1 are redundant.  N-1
		 * PCI roots should be skipped per DF/SMN interface so
		 * the following DF/SMN interfaces get mapped to
		 * correct PCI roots.
		 */
Does that read clearer?

-- 
Brian Woods