linux-kernel - Re: [PATCH v3] PCI: Prevent power state transition of erroneous device

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Message-ID: <aCInTU5BmL0botSd@black.fi.intel.com>
Date: Mon, 12 May 2025 19:52:29 +0300
From: Raag Jadav <raag.jadav@...el.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: mahesh@...ux.ibm.com, oohall@...il.com, bhelgaas@...gle.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	ilpo.jarvinen@...ux.intel.com, lukas@...ner.de,
	aravind.iddamsetty@...ux.intel.com, linux-pm@...r.kernel.org
Subject: Re: [PATCH v3] PCI: Prevent power state transition of erroneous
 device

On Mon, May 12, 2025 at 01:56:06PM +0200, Rafael J. Wysocki wrote:
> On Sun, May 4, 2025 at 11:06 AM Raag Jadav <raag.jadav@...el.com> wrote:
> >
> > If error flags are set on an AER capable device, most likely either the
> > device recovery is in progress or has already failed. Neither of the
> > cases are well suited for power state transition of the device, since
> > this can lead to unpredictable consequences like resume failure, or in
> > worst case the device is lost because of it. Leave the device in its
> > existing power state to avoid such issues.
> >
> > Signed-off-by: Raag Jadav <raag.jadav@...el.com>
> > ---
> >
> > v2: Synchronize AER handling with PCI PM (Rafael)
> > v3: Move pci_aer_in_progress() to pci_set_low_power_state() (Rafael)
> >     Elaborate "why" (Bjorn)
> 
> I think this is reasonable, so
> 
> Acked-by: Rafael J. Wysocki <rafael@...nel.org>

Thank you!

> (and you might as well CC it to linux-pm@...r.kernel.org>).

Cc'ing linux-pm list as requested by Rafael.

> > More discussion on [1].
> > [1] https://lore.kernel.org/all/CAJZ5v0g-aJXfVH+Uc=9eRPuW08t-6PwzdyMXsC6FZRKYJtY03Q@mail.gmail.com/
> >
> >  drivers/pci/pci.c      | 12 ++++++++++++
> >  drivers/pci/pcie/aer.c | 11 +++++++++++
> >  include/linux/aer.h    |  2 ++
> >  3 files changed, 25 insertions(+)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 4d7c9f64ea24..25b2df34336c 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -9,6 +9,7 @@
> >   */
> >
> >  #include <linux/acpi.h>
> > +#include <linux/aer.h>
> >  #include <linux/kernel.h>
> >  #include <linux/delay.h>
> >  #include <linux/dmi.h>
> > @@ -1539,6 +1540,17 @@ static int pci_set_low_power_state(struct pci_dev *dev, pci_power_t state, bool
> >            || (state == PCI_D2 && !dev->d2_support))
> >                 return -EIO;
> >
> > +       /*
> > +        * If error flags are set on an AER capable device, most likely either
> > +        * the device recovery is in progress or has already failed. Neither of
> > +        * the cases are well suited for power state transition of the device,
> > +        * since this can lead to unpredictable consequences like resume
> > +        * failure, or in worst case the device is lost because of it. Leave the
> > +        * device in its existing power state to avoid such issues.
> > +        */
> > +       if (pci_aer_in_progress(dev))
> > +               return -EIO;
> > +
> >         pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
> >         if (PCI_POSSIBLE_ERROR(pmcsr)) {
> >                 pci_err(dev, "Unable to change power state from %s to %s, device inaccessible\n",
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index a1cf8c7ef628..4040770df4f0 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -237,6 +237,17 @@ int pcie_aer_is_native(struct pci_dev *dev)
> >  }
> >  EXPORT_SYMBOL_NS_GPL(pcie_aer_is_native, "CXL");
> >
> > +bool pci_aer_in_progress(struct pci_dev *dev)
> > +{
> > +       u16 reg16;
> > +
> > +       if (!pcie_aer_is_native(dev))
> > +               return false;
> > +
> > +       pcie_capability_read_word(dev, PCI_EXP_DEVSTA, &reg16);
> > +       return !!(reg16 & PCI_EXP_AER_FLAGS);
> > +}
> > +
> >  static int pci_enable_pcie_error_reporting(struct pci_dev *dev)
> >  {
> >         int rc;
> > diff --git a/include/linux/aer.h b/include/linux/aer.h
> > index 02940be66324..e6a380bb2e68 100644
> > --- a/include/linux/aer.h
> > +++ b/include/linux/aer.h
> > @@ -56,12 +56,14 @@ struct aer_capability_regs {
> >  #if defined(CONFIG_PCIEAER)
> >  int pci_aer_clear_nonfatal_status(struct pci_dev *dev);
> >  int pcie_aer_is_native(struct pci_dev *dev);
> > +bool pci_aer_in_progress(struct pci_dev *dev);
> >  #else
> >  static inline int pci_aer_clear_nonfatal_status(struct pci_dev *dev)
> >  {
> >         return -EINVAL;
> >  }
> >  static inline int pcie_aer_is_native(struct pci_dev *dev) { return 0; }
> > +static inline bool pci_aer_in_progress(struct pci_dev *dev) { return false; }
> >  #endif
> >
> >  void pci_print_aer(struct pci_dev *dev, int aer_severity,
> > --
> > 2.34.1
> >