Subject: Re: [PATCH] powerpc/pseries/eeh: move pseries_eeh_err_inject() outside CONFIG_DEBUG_FS block

From: Ritesh Harjani (IBM) <[email-masked]>
Date: Wed, 18 Sep 2024 08:03:56 +0530

Narayana Murty N <[email-masked]> writes:

> Makes pseries_eeh_err_inject() available even when debugfs
> is disabled (CONFIG_DEBUG_FS=n). It moves eeh_debugfs_break_device()
> and eeh_pe_inject_mmio_error() out of the CONFIG_DEBUG_FS block
> and renames it as eeh_break_device().
>
> Reported-by: kernel test robot <[email-masked]>
> Closes: https://lore.kernel.org/oe-kbuild-all/[email-masked]/
> Fixes: b0e2b828dfca ("powerpc/pseries/eeh: Fix pseries_eeh_err_inject")
> Signed-off-by: Narayana Murty N <[email-masked]>
> ---
>  arch/powerpc/kernel/eeh.c | 198 +++++++++++++++++++-------------------
>  1 file changed, 99 insertions(+), 99 deletions(-)

Ok, so in your original patch you implemented eeh_inject ops for pseries
using mmio based eeh error injection (eeh_pe_inject_mmio_error()), which
uses the functions defined under debugfs -> eeh_debugfs_break_device(). 

This was failing when CONFIG_DEBUGFS is not defined, thus referring to
undefined function definition. 

Minor nit below.

>
> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
> index 49ab11a287a3..0fe25e907ea6 100644
> --- a/arch/powerpc/kernel/eeh.c
> +++ b/arch/powerpc/kernel/eeh.c
> @@ -1574,6 +1574,104 @@ static int proc_eeh_show(struct seq_file *m, void *v)
>  }
>  #endif /* CONFIG_PROC_FS */
>  
> +static int eeh_break_device(struct pci_dev *pdev)
> +{
> +	struct resource *bar = NULL;
> +	void __iomem *mapped;
> +	u16 old, bit;
> +	int i, pos;
> +
> +	/* Do we have an MMIO BAR to disable? */
> +	for (i = 0; i <= PCI_STD_RESOURCE_END; i++) {
> +		struct resource *r = &pdev->resource[i];
> +
> +		if (!r->flags || !r->start)
> +			continue;
> +		if (r->flags & IORESOURCE_IO)
> +			continue;
> +		if (r->flags & IORESOURCE_UNSET)
> +			continue;
> +
> +		bar = r;
> +		break;
> +	}
> +
> +	if (!bar) {
> +		pci_err(pdev, "Unable to find Memory BAR to cause EEH with\n");
> +		return -ENXIO;
> +	}
> +
> +	pci_err(pdev, "Going to break: %pR\n", bar);
> +
> +	if (pdev->is_virtfn) {
> +#ifndef CONFIG_PCI_IOV
> +		return -ENXIO;
> +#else
> +		/*
> +		 * VFs don't have a per-function COMMAND register, so the best
> +		 * we can do is clear the Memory Space Enable bit in the PF's
> +		 * SRIOV control reg.
> +		 *
> +		 * Unfortunately, this requires that we have a PF (i.e doesn't
> +		 * work for a passed-through VF) and it has the potential side
> +		 * effect of also causing an EEH on every other VF under the
> +		 * PF. Oh well.
> +		 */
> +		pdev = pdev->physfn;
> +		if (!pdev)
> +			return -ENXIO; /* passed through VFs have no PF */
> +
> +		pos  = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_SRIOV);
> +		pos += PCI_SRIOV_CTRL;
> +		bit  = PCI_SRIOV_CTRL_MSE;
> +#endif /* !CONFIG_PCI_IOV */
> +	} else {
> +		bit = PCI_COMMAND_MEMORY;
> +		pos = PCI_COMMAND;
> +	}
> +
> +	/*
> +	 * Process here is:
> +	 *
> +	 * 1. Disable Memory space.
> +	 *
> +	 * 2. Perform an MMIO to the device. This should result in an error
> +	 *    (CA  / UR) being raised by the device which results in an EEH
> +	 *    PE freeze. Using the in_8() accessor skips the eeh detection hook
> +	 *    so the freeze hook so the EEH Detection machinery won't be
> +	 *    triggered here. This is to match the usual behaviour of EEH
> +	 *    where the HW will asynchronously freeze a PE and it's up to
> +	 *    the kernel to notice and deal with it.
> +	 *
> +	 * 3. Turn Memory space back on. This is more important for VFs
> +	 *    since recovery will probably fail if we don't. For normal
> +	 *    the COMMAND register is reset as a part of re-initialising
> +	 *    the device.
> +	 *
> +	 * Breaking stuff is the point so who cares if it's racy ;)
> +	 */
> +	pci_read_config_word(pdev, pos, &old);
> +
> +	mapped = ioremap(bar->start, PAGE_SIZE);
> +	if (!mapped) {
> +		pci_err(pdev, "Unable to map MMIO BAR %pR\n", bar);
> +		return -ENXIO;
> +	}
> +
> +	pci_write_config_word(pdev, pos, old & ~bit);
> +	in_8(mapped);
> +	pci_write_config_word(pdev, pos, old);
> +
> +	iounmap(mapped);
> +
> +	return 0;
> +}
> +
> +int eeh_pe_inject_mmio_error(struct pci_dev *pdev)
> +{
> +	return eeh_break_device(pdev);
> +}
> +

Why have an extra eeh_pe_inject_mmio_error() function which only calls
eeh_break_device()?

Maybe we can rename eeh_break_device() to eeh_mmio_break_device() and use
this function itself at both call sites?

-ritesh