linux-kernel - Re: [PATCH v4] PCI: Prevent power state transition of erroneous device

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Message-ID: <aCsK743YSuahPtnH@black.fi.intel.com>
Date: Mon, 19 May 2025 13:41:51 +0300
From: Raag Jadav <raag.jadav@...el.com>
To: rafael@...nel.org, mahesh@...ux.ibm.com, oohall@...il.com,
	bhelgaas@...gle.com
Cc: linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, ilpo.jarvinen@...ux.intel.com,
	lukas@...ner.de, aravind.iddamsetty@...ux.intel.com,
	superm1@...nel.org, benato.denis96@...il.com
Subject: Re: [PATCH v4] PCI: Prevent power state transition of erroneous
 device

On Mon, May 19, 2025 at 03:58:08PM +0530, Raag Jadav wrote:
> If error status is 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)
> v4: Rely on error status instead of device status
>     Condense comment (Lukas)

Since pci_aer_in_progress() is changed I've not included Rafael's tag with
my understanding of this needing a revisit. If this was a mistake, please
let me know.

Denis, Mario, does this fix your issue?

> More discussion on [1].
> [1] https://lore.kernel.org/all/CAJZ5v0g-aJXfVH+Uc=9eRPuW08t-6PwzdyMXsC6FZRKYJtY03Q@mail.gmail.com/
> 
>  drivers/pci/pci.c      |  9 +++++++++
>  drivers/pci/pcie/aer.c | 13 +++++++++++++
>  include/linux/aer.h    |  2 ++
>  3 files changed, 24 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 4d7c9f64ea24..a20018692933 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 +1540,14 @@ 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 status is set on an AER capable device, it is not well
> +	 * suited for power state transition. Leave it in its existing power
> +	 * state to avoid issues like unpredictable resume failure.
> +	 */
> +	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..617fbac0d38a 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -237,6 +237,19 @@ 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)
> +{
> +	int aer = dev->aer_cap;
> +	u32 cor, uncor;
> +
> +	if (!pcie_aer_is_native(dev))
> +		return false;
> +
> +	pci_read_config_dword(dev, aer + PCI_ERR_COR_STATUS, &cor);
> +	pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, &uncor);
> +	return cor || uncor;
> +}
> +
>  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
>