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

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Date:   Mon, 5 Nov 2018 22:42:33 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Woods, Brian" <Brian.Woods@....com>
Cc:     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 08:33:34PM +0000, Woods, Brian wrote:
> I think having them togeter is cleaner. If you aren't finding any
> misc IDs, I highly doubt you'll find any root IDs.  There shouldn't
> be much of a difference in how fast the function exits, either way.
> If you want it the other way though, I don't mind changing it.

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.

> Would
> 
> 		/*
> 		 * 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.  The
> 		 * N-1 PCI roots should be skipped per DF/SMN interface
> 		 * so the DF/SMN interfaces get mapped to the correct
> 		 * PCI root.

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.