linux-kernel - Re: [PATCH] iommu: Remove stack trace from broken irq remapping warning

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Date:	Fri, 27 Sep 2013 12:24:10 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Neil Horman <nhorman@...driver.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Joerg Roedel <joro@...tes.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
Subject: Re: [PATCH] iommu: Remove stack trace from broken irq remapping warning

On Fri, Sep 27, 2013 at 9:53 AM, Neil Horman <nhorman@...driver.com> wrote:
> The warning for the irq remapping broken check in intel_irq_remapping.c is
> pretty pointless.  We need the warning, but we know where its comming from, the
> stack trace will always be the same, and it needlessly triggers things like
> Abrt.  This changes the warning to just print a text warning about BIOS being
> broken, without the stack trace, then sets the appropriate taint bit.  Since we
> automatically disable irq remapping, theres no need to contiue making Abrt jump
> at this problem
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
> CC: Joerg Roedel <joro@...tes.org>
> CC: Bjorn Helgaas <bhelgaas@...gle.com>
> CC: Andy Lutomirski <luto@...capital.net>
> CC: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> CC: Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
> ---
>  drivers/iommu/intel_irq_remapping.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
> index f71673d..b97d70b 100644
> --- a/drivers/iommu/intel_irq_remapping.c
> +++ b/drivers/iommu/intel_irq_remapping.c
> @@ -525,12 +525,13 @@ static int __init intel_irq_remapping_supported(void)
>         if (disable_irq_remap)
>                 return 0;
>         if (irq_remap_broken) {
> -               WARN_TAINT(1, TAINT_FIRMWARE_WORKAROUND,
> -                          "This system BIOS has enabled interrupt remapping\n"
> -                          "on a chipset that contains an erratum making that\n"
> -                          "feature unstable.  To maintain system stability\n"
> -                          "interrupt remapping is being disabled.  Please\n"
> -                          "contact your BIOS vendor for an update\n");
> +               printk(KERN_WARNING
> +                       "This system BIOS has enabled interrupt remapping\n"
> +                       "on a chipset that contains an erratum making that\n"
> +                       "feature unstable.  To maintain system stability\n"
> +                       "interrupt remapping is being disabled.  Please\n"
> +                       "contact your BIOS vendor for an update\n");
> +               add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);

Is the taint bit actually useful?  It seems like functionality will be
missing if this workaround happens, but everything should be stable.

--Andy
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