[PATCH 12/14] powerpc/eeh: Add debugfs interface to run an EEH check

[Sam Bobroff]

On Tue, Sep 03, 2019 at 08:16:03PM +1000, Oliver O'Halloran wrote:
> Detecting an frozen EEH PE usually occurs when an MMIO load returns a 0xFFs
> response. When performing EEH testing using the EEH error injection feature
> available on some platforms there is no simple way to kick-off the kernel's
> recovery process since any accesses from userspace (usually /dev/mem) will
> bypass the MMIO helpers in the kernel which check if a 0xFF response is due
> to an EEH freeze or not.
> 
> If a device contains a 0xFF byte in it's config space it's possible to
> trigger the recovery process via config space read from userspace, but this
> is not a reliable method. If a driver is bound to the device an in use it
> will frequently trigger the MMIO check, but this is also inconsistent.
> 
> To solve these problems this patch adds a debugfs file called
> "eeh_dev_check" which accepts a <domain>:<bus>:<dev>.<fn> string and runs
> eeh_dev_check_failure() on it. This is the same check that's done when the
> kernel gets a 0xFF result from an config or MMIO read with the added
> benifit that it can be reliably triggered from userspace.
> 
> Signed-off-by: Oliver O'Halloran <oohall at gmail.com>

Looks good, and I tested it with the next patch and it seems to work.

But I think you should make it clear that this does not work with
the hardware "EEH error injection" facility accessible via debugfs in
err_injct (that doesn't seem clear to me from the commit message).

Tested-by: Sam Bobroff <sbobroff at linux.ibm.com>
Reviewed-by: Sam Bobroff <sbobroff at linux.ibm.com>
> ---
>  arch/powerpc/kernel/eeh.c | 61 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
> index 46d17817b438..ace1c5a6b8ed 100644
> --- a/arch/powerpc/kernel/eeh.c
> +++ b/arch/powerpc/kernel/eeh.c
> @@ -1873,6 +1873,64 @@ static const struct file_operations eeh_force_recover_fops = {
>  	.llseek	= no_llseek,
>  	.write	= eeh_force_recover_write,
>  };
> +
> +static ssize_t eeh_debugfs_dev_usage(struct file *filp,
> +				char __user *user_buf,
> +				size_t count, loff_t *ppos)
> +{
> +	static const char usage[] = "input format: <domain>:<bus>:<dev>.<fn>\n";
> +
> +	return simple_read_from_buffer(user_buf, count, ppos,
> +				       usage, sizeof(usage) - 1);
> +}
> +
> +static ssize_t eeh_dev_check_write(struct file *filp,
> +				const char __user *user_buf,
> +				size_t count, loff_t *ppos)
> +{
> +	uint32_t domain, bus, dev, fn;
> +	struct pci_dev *pdev;
> +	struct eeh_dev *edev;
> +	char buf[20];
> +	int ret;
> +
> +	ret = simple_write_to_buffer(buf, sizeof(buf), ppos, user_buf, count);
> +	if (!ret)
> +		return -EFAULT;
> +
> +	ret = sscanf(buf, "%x:%x:%x.%x", &domain, &bus, &dev, &fn);
> +	if (ret != 4) {
> +		pr_err("%s: expected 4 args, got %d\n", __func__, ret);
> +		return -EINVAL;
> +	}
> +
> +	pdev = pci_get_domain_bus_and_slot(domain, bus, (dev << 3) | fn);
> +	if (!pdev)
> +		return -ENODEV;
> +
> +	edev = pci_dev_to_eeh_dev(pdev);
> +	if (!edev) {
> +		pci_err(pdev, "No eeh_dev for this device!\n");
> +		pci_dev_put(pdev);
> +		return -ENODEV;
> +	}
> +
> +	ret = eeh_dev_check_failure(edev);
> +	pci_info(pdev, "eeh_dev_check_failure(%04x:%02x:%02x.%01x) = %d\n",
> +			domain, bus, dev, fn, ret);
> +
> +	pci_dev_put(pdev);
> +
> +	return count;
> +}
> +
> +static const struct file_operations eeh_dev_check_fops = {
> +	.open	= simple_open,
> +	.llseek	= no_llseek,
> +	.write	= eeh_dev_check_write,
> +	.read   = eeh_debugfs_dev_usage,
> +};
> +
>  #endif
>  
>  static int __init eeh_init_proc(void)
> @@ -1888,6 +1946,9 @@ static int __init eeh_init_proc(void)
>  		debugfs_create_bool("eeh_disable_recovery", 0600,
>  				powerpc_debugfs_root,
>  				&eeh_debugfs_no_recover);
> +		debugfs_create_file_unsafe("eeh_dev_check", 0600,
> +				powerpc_debugfs_root, NULL,
> +				&eeh_dev_check_fops);
>  		debugfs_create_file_unsafe("eeh_force_recover", 0600,
>  				powerpc_debugfs_root, NULL,
>  				&eeh_force_recover_fops);
> -- 
> 2.21.0
> 
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