linux-kernel - Re: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain

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Message-Id: <08080FC7-861B-472A-BD7D-02D33926677F@canonical.com>
Date:   Tue, 25 Aug 2020 14:39:55 +0800
From:   Kai Heng Feng <kai.heng.feng@...onical.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, jonathan.derrick@...el.com,
        Mario.Limonciello@...l.com, Heiner Kallweit <hkallweit1@...il.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Krzysztof Wilczynski <kw@...ux.com>,
        "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        "Huffman, Amber" <amber.huffman@...el.com>
Subject: Re: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain

Hi Christoph,

> On Aug 25, 2020, at 2:23 PM, Christoph Hellwig <hch@...radead.org> wrote:
> 
> On Fri, Aug 21, 2020 at 08:32:20PM +0800, Kai-Heng Feng wrote:
>> New Intel laptops with VMD cannot reach deeper power saving state,
>> renders very short battery time.
> 
> So what about just disabling VMD given how bloody pointless it is?
> Hasn't anyone learned from the AHCI remapping debacle?
> 
> I'm really pissed at all this pointless crap intel comes up with just
> to make life hard for absolutely no gain.  Is it so hard to just leave
> a NVMe device as a standard NVMe device instead of f*^&ing everything
> up in the chipset to make OS support a pain and I/O slower than by
> doing nothing?

>From what I can see from the hardwares at my hand, VMD only enables a PCI domain and PCI bridges behind it.

NVMe works as a regular NVMe under those bridges. No magic remapping happens here.

Kai-Heng