Re: [PATCH] iommu/vt-d: quirk_ioat_snb_local_iommu: replace WARN_TAINT with pr_warn + add_taint

From: Lu Baolu <baolu.lu@linux.intel.com>
To: Hans de Goede <hdegoede@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org
Subject: Re: [PATCH] iommu/vt-d: quirk_ioat_snb_local_iommu: replace WARN_TAINT with pr_warn + add_taint
Date: Tue, 10 Mar 2020 09:46:06 +0800	[thread overview]
Message-ID: <4e4a73d0-50db-49fa-0e46-468032bf9775@linux.intel.com> (raw)
In-Reply-To: <20200309182510.373875-1-hdegoede@redhat.com>

On 2020/3/10 2:25, Hans de Goede wrote:
> Quoting from the comment describing the WARN functions in
> include/asm-generic/bug.h:
> 
>   * WARN(), WARN_ON(), WARN_ON_ONCE, and so on can be used to report
>   * significant kernel issues that need prompt attention if they should ever
>   * appear at runtime.
>   *
>   * Do not use these macros when checking for invalid external inputs
> 
> The (buggy) firmware tables which the dmar code was calling WARN_TAINT
> for really are invalid external inputs. They are not under the kernel's
> control and the issues in them cannot be fixed by a kernel update.
> So logging a backtrace, which invites bug reports to be filed about this,
> is not helpful.
> 
> BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=701847
> Fixes: 556ab45f9a77 ("ioat2: catch and recover from broken vtd configurations v6")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu

> ---
>   drivers/iommu/intel-iommu.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 3857a5cd1a75..8fd132f8e885 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -4261,10 +4261,11 @@ static void quirk_ioat_snb_local_iommu(struct pci_dev *pdev)
>   
>   	/* we know that the this iommu should be at offset 0xa000 from vtbar */
>   	drhd = dmar_find_matched_drhd_unit(pdev);
> -	if (WARN_TAINT_ONCE(!drhd || drhd->reg_base_addr - vtbar != 0xa000,
> -			    TAINT_FIRMWARE_WORKAROUND,
> -			    "BIOS assigned incorrect VT-d unit for Intel(R) QuickData Technology device\n"))
> +	if (!drhd || drhd->reg_base_addr - vtbar != 0xa000) {
> +		pr_warn_once(FW_BUG "BIOS assigned incorrect VT-d unit for Intel(R) QuickData Technology device\n");
> +		add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
>   		pdev->dev.archdata.iommu = DUMMY_DEVICE_DOMAIN_INFO;
> +	}
>   }
>   DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_IOAT_SNB, quirk_ioat_snb_local_iommu);
>   
> 
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