linux-kernel - Re: [PATCH 2/2] PCI: vmd: Let OS control ASPM for devices under VMD domain

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAAd53p66NNOaD=KdvW911gKSf+QOSCik9c-dJmn6zQqXaoFQXw@mail.gmail.com>
Date: Fri, 2 Aug 2024 09:04:21 +0800
From: Kai-Heng Feng <kai.heng.feng@...onical.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org, nirmal.patel@...ux.intel.com, 
	jonathan.derrick@...ux.dev, ilpo.jarvinen@...ux.intel.com, 
	david.e.box@...ux.intel.com
Subject: Re: [PATCH 2/2] PCI: vmd: Let OS control ASPM for devices under VMD domain

On Fri, Aug 2, 2024 at 8:04 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Thu, May 30, 2024 at 04:52:27PM +0800, Kai-Heng Feng wrote:
> > Intel SoC cannot reach lower power states when mapped VMD PCIe bridges
> > and NVMe devices don't have ASPM configured.
> >
> > So set aspm_os_control attribute to let OS really enable ASPM for those
> > devices.
> >
> > Fixes: f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
>
> I assume f492edb40b54 was tested and worked at the time.  Is the
> implication that newer Intel SoCs have added more requirements for
> getting to low power states, since __pci_enable_link_state() would
> have warned and done nothing even then?
>
> Or maybe this is a new system that sets ACPI_FADT_NO_ASPM, and
> f492edb40b54 was tested on systems that did *not* set
> ACPI_FADT_NO_ASPM?

I believe it's the case here. Vendors may or may not set
ACPI_FADT_NO_ASPM, so f492edb40b54 works on some systems but not
others.

Kai-Heng

>
> > Link: https://lore.kernel.org/linux-pm/218aa81f-9c6-5929-578d-8dc15f83dd48@panix.com/
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > ---
> >  drivers/pci/controller/vmd.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> > index 87b7856f375a..1dbc525c473f 100644
> > --- a/drivers/pci/controller/vmd.c
> > +++ b/drivers/pci/controller/vmd.c
> > @@ -751,6 +751,8 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
> >       if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
> >               return 0;
> >
> > +     pdev->aspm_os_control = 1;
> > +
> >       pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
> >
> >       pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
> > --
> > 2.43.0
> >