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

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Message-ID: <CAJZ5v0hgpq0VmO_rDnEjDQniUiLJP3yo3-Rpy1NNxA_k8VAS2A@mail.gmail.com>
Date: Mon, 12 May 2025 13:56:06 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Raag Jadav <raag.jadav@...el.com>
Cc: rafael@...nel.org, 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
Subject: Re: [PATCH v3] PCI: Prevent power state transition of erroneous device

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>

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

Thanks!

>
> 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
>