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

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Message-ID: <DM6PR19MB2636ACECA16E43638B502A6DFA550@DM6PR19MB2636.namprd19.prod.outlook.com>
Date:   Thu, 27 Aug 2020 17:49:40 +0000
From:   "Limonciello, Mario" <Mario.Limonciello@...l.com>
To:     "hch@...radead.org" <hch@...radead.org>,
        "Derrick, Jonathan" <jonathan.derrick@...el.com>
CC:     "wangxiongfeng2@...wei.com" <wangxiongfeng2@...wei.com>,
        "kw@...ux.com" <kw@...ux.com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "kai.heng.feng@...onical.com" <kai.heng.feng@...onical.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "Huffman, Amber" <amber.huffman@...el.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>
Subject: RE: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain

> > I don't see the purpose of this line of discussion. VMD has been in the
> > kernel for 5 years. We are constantly working on better support.
> 
> Please just work with the platform people to allow the host to disable
> VMD.  That is the only really useful value add here.

Can you further elaborate what exactly you're wanting here?  VMD enable/disable
is something that is configured in firmware setup as the firmware does the early
configuration for the silicon related to it.  So it's up to the OEM whether to
offer the knob to an end user.

At least for Dell this setting also does export to sysfs and can be turned on/off
around a reboot cycle via this: https://patchwork.kernel.org/patch/11693231/.

As was mentioned earlier in this thread VMD is likely to be defaulting to "on"
for many machines with the upcoming silicon.  Making it work well on Linux is
preferable to again having to change firmware settings between operating systems
like the NVME remapping thing from earlier silicon required.