linux-kernel - Re: BUG in drivers/dma/ioat/dma

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Date:	Thu, 01 Jul 2010 09:15:36 +0100
From:	David Woodhouse <David.Woodhouse@...el.com>
To:	"Williams, Dan J" <dan.j.williams@...el.com>
Cc:	Chris Li <lkml@...isli.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: BUG in drivers/dma/ioat/dma_v2.c:314

On Thu, 2010-07-01 at 08:26 +0100, Williams, Dan J wrote:
> On 7/1/2010 12:12 AM, Woodhouse, David wrote:
> > On Thu, 2010-07-01 at 07:51 +0100, Williams, Dan J wrote:
> >> This version of the device only exists on the 5400 chipset and always
> >> has its own iommu, but since other platforms get the DMAR entry right I
> >> think this hammer is too big?  Wouldn't this break VT-d operation on
> >> non-busted platforms?
> >
> > That just means we have to get the quirk right. Does 'this version' of
> > the device have its own PCI ID? We can always fall back to checking the
> > ID of the device at 0000:00:00.0 to check which chipset we're on.
> >
> 
> PCI_DEVICE_ID_INTEL_IOAT_SNB only exists on this chipset 

Something like this, then?

diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 0a19708..24ac178 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -543,8 +543,20 @@ dmar_find_matched_drhd_unit(struct pci_dev *dev)
 				    header);
 
 		if (dmaru->include_all &&
-		    drhd->segment == pci_domain_nr(dev->bus))
+		    drhd->segment == pci_domain_nr(dev->bus)) {
+			/* We know that this device on this chipset has its own
+			   IOMMU. If we find it under the catch-all IOMMU, then
+			   the BIOS is lying to us. Hope that the IOMMU for
+			   this device is actually disabled, and it needs no
+			   translation... */
+			if (dev->vendor == PCI_VENDOR_ID_INTEL &&
+			    dev->device == PCI_DEVICE_ID_INTEL_IOAT_SNB) {
+				WARN_TAINT_ONCE(1, TAINT_FIRMWARE_WORKAROUND,
+						"BIOS wrongly included I/OAT device under catch-all VT-d unit\n");
+				return NULL;
+			}
 			return dmaru;
+		}
 
 		if (dmar_pci_device_match(dmaru->devices,
 					  dmaru->devices_cnt, dev))


-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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