From: Christoph Hellwig <hch@infradead.org>
To: Kai Heng Feng <kai.heng.feng@canonical.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Bjorn Helgaas <bhelgaas@google.com>,
jonathan.derrick@intel.com, Mario.Limonciello@dell.com,
Heiner Kallweit <hkallweit1@gmail.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Xiongfeng Wang <wangxiongfeng2@huawei.com>,
Krzysztof Wilczynski <kw@linux.com>,
"open list:PCI SUBSYSTEM" <linux-pci@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
"Huffman, Amber" <amber.huffman@intel.com>
Subject: Re: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain
Date: Tue, 25 Aug 2020 07:56:34 +0100 [thread overview]
Message-ID: <20200825065634.GA2691@infradead.org> (raw)
In-Reply-To: <08080FC7-861B-472A-BD7D-02D33926677F@canonical.com>
On Tue, Aug 25, 2020 at 02:39:55PM +0800, Kai Heng Feng wrote:
> Hi Christoph,
>
> > On Aug 25, 2020, at 2:23 PM, Christoph Hellwig <hch@infradead.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.
It definitively is less bad than the AHCI remapping, that is for sure.
But it still requires:
- a new OS driver just to mak the PCIe device show up
- indirections in the irq handling
- indirections in the DMA handling
- hacks for ASPSM
- hacks for X (there were a few more)
while adding absolutely no value. Basically we have to add a large
chunk of kernel code just to undo silicone/firmware Intel added to their
platform to make things complicated. I mean it is their platform and if
they want a "make things complicated" option that is fine, but it should
not be on by default.
next prev parent reply other threads:[~2020-08-25 6:56 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 12:32 [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain Kai-Heng Feng
2020-08-24 13:04 ` Mika Westerberg
2020-08-25 6:23 ` Christoph Hellwig
2020-08-25 6:39 ` Kai Heng Feng
2020-08-25 6:56 ` Christoph Hellwig [this message]
2020-08-26 5:53 ` Kai-Heng Feng
2020-09-02 19:48 ` David Fugate
2020-09-02 22:54 ` Keith Busch
2020-08-26 21:43 ` Derrick, Jonathan
2020-08-27 6:34 ` hch
2020-08-27 16:13 ` Derrick, Jonathan
2020-08-27 16:23 ` hch
2020-08-27 16:45 ` Derrick, Jonathan
2020-08-27 16:50 ` hch
2020-08-27 21:33 ` Dan Williams
2020-08-29 7:23 ` hch
2020-08-27 17:49 ` Limonciello, Mario
2020-08-29 7:24 ` hch
2020-09-10 1:55 ` Bjorn Helgaas
2020-09-10 16:33 ` Derrick, Jonathan
2020-09-10 17:38 ` Bjorn Helgaas
[not found] <0f902d555deb423ef1c79835b23c917be2633162.camel@intel.com>
2020-09-10 19:17 ` Bjorn Helgaas
2020-09-10 19:51 ` Derrick, Jonathan
2020-09-17 17:20 ` Bjorn Helgaas
2020-09-23 14:29 ` Kai-Heng Feng
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