linux-kernel - Re: [PATCH v7 6/9] s390/pci: Store PCI error information for passthrough devices

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Message-ID: <99b0c4dd03013226c8e3fa9dc6661f40fc1b0b88.camel@linux.ibm.com>
Date: Tue, 20 Jan 2026 23:34:05 +0100
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Farhan Ali <alifm@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Cc: helgaas@...nel.org, lukas@...ner.de, alex@...zbot.org, clg@...hat.com,
        stable@...r.kernel.org, mjrosato@...ux.ibm.com
Subject: Re: [PATCH v7 6/9] s390/pci: Store PCI error information for
 passthrough devices

On Wed, 2026-01-07 at 10:32 -0800, Farhan Ali wrote:
> For a passthrough device we need co-operation from user space to recover
> the device. This would require to bubble up any error information to user
> space.  Let's store this error information for passthrough devices, so it
> can be retrieved later.
> 
> Signed-off-by: Farhan Ali <alifm@...ux.ibm.com>
> ---
>  arch/s390/include/asm/pci.h      | 28 ++++++++++
>  arch/s390/pci/pci.c              |  1 +
>  arch/s390/pci/pci_event.c        | 95 +++++++++++++++++++-------------
>  drivers/vfio/pci/vfio_pci_zdev.c |  2 +
>  4 files changed, 88 insertions(+), 38 deletions(-)
> 
> 
--- snip ---
>  
> +static void zpci_store_pci_error(struct pci_dev *pdev,
> +				 struct zpci_ccdf_err *ccdf)
> +{
> +	struct zpci_dev *zdev = to_zpci(pdev);
> +	int i;
> +
> +	mutex_lock(&zdev->pending_errs_lock);
> +	if (zdev->pending_errs.count >= ZPCI_ERR_PENDING_MAX) {
> +		pr_err("%s: Maximum number (%d) of pending error events queued",
> +				pci_name(pdev), ZPCI_ERR_PENDING_MAX);

Nit: Here and in a few other places the alignment doesn't match the
open parenthesis. These are caught by checkpatch.pl with "--strict".
That also points out a couple of lines over 75 characters in commit
messages in this series.

> +		mutex_unlock(&zdev->pending_errs_lock);
> +		return;
> +	}
> +
> +	i = zdev->pending_errs.tail % ZPCI_ERR_PENDING_MAX;
> +	memcpy(&zdev->pending_errs.err[i], ccdf, sizeof(struct zpci_ccdf_err));
> +	zdev->pending_errs.tail++;
> +	zdev->pending_errs.count++;
> +	mutex_unlock(&zdev->pending_errs_lock);
> +}
> +
> +void zpci_cleanup_pending_errors(struct zpci_dev *zdev)
> +{
> +	struct pci_dev *pdev = NULL;
> +
> +	mutex_lock(&zdev->pending_errs_lock);
> +	pdev = pci_get_slot(zdev->zbus->bus, zdev->devfn);
> +	if (zdev->pending_errs.count)
> +		pr_info("%s: Unhandled PCI error events count=%d",
> +				pci_name(pdev), zdev->pending_errs.count);

Nit: Align with open parenthesis (see above)

> +	memset(&zdev->pending_errs, 0, sizeof(struct zpci_ccdf_pending));
> +	pci_dev_put(pdev);

Yay, the previously missing pci_dev_put()

> +	mutex_unlock(&zdev->pending_errs_lock);
> +}
> +EXPORT_SYMBOL_GPL(zpci_cleanup_pending_errors);
> +
> 
--- snip ---
> @@ -210,12 +223,23 @@ static pci_ers_result_t zpci_event_attempt_error_recovery(struct pci_dev *pdev)
>  		goto out_unlock;
>  	}
>  
> +	if (needs_mediated_recovery(pdev))
> +		zpci_store_pci_error(pdev, ccdf);
> +
>  	ers_res = zpci_event_notify_error_detected(pdev, driver);
>  	if (ers_result_indicates_abort(ers_res)) {
>  		status_str = "failed (abort on detection)";
>  		goto out_unlock;
>  	}
>  
> +	if (needs_mediated_recovery(pdev)) {
> +		pr_info("%s: Leaving recovery of pass-through device to user-space\n",
> +				pci_name(pdev));

Nit: Code alignment

> +		ers_res = PCI_ERS_RESULT_RECOVERED;
> +		status_str = "in progress";
> +		goto out_unlock;
> +	}
> +

With the style issues fixed feel free to add my:

Reviewed-by: Niklas Schnelle <schnelle@...ux.ibm.com>