[RESEND PATCH] iommu/intel: GAW only gets smaller by adding devices

From: Alex Williamson
Date: Tue Jul 08 2014 - 11:42:28 EST

As analyzed in https://bugzilla.kernel.org/show_bug.cgi?id=76331
we can have multiple DRHDs in a system and each may support different
guest address widths. We can add a device behind a less capable DRHD
to a domain so long as the lesser DRHD can map the existing domain
page table. We should never increase the address width as a result
of adding a device to the domain. The current code simply updates
the width to the last added device. Change to keep it at the
minumum DRHD width.

Reported-by: mspeder@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Tested-by: mspeder@xxxxxxxxxxxxxxxxxxxxx
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>

I can't find any evidence that this got picked, resending.

drivers/iommu/intel-iommu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 6ad29ed..3458bc8 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4309,7 +4309,7 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
__func__, addr_width, dmar_domain->max_addr);
return -EFAULT;
- dmar_domain->gaw = addr_width;
+ dmar_domain->gaw = min(addr_width, dmar_domain->gaw);

* Knock out extra levels of page tables if necessary

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