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intel-iommu: ignore page table validation in pass through mode 

We are seeing a bug when booting w/ iommu=pt with current upstream
(bisect blames 19943b0e30 "intel-iommu:
Unify hardware and software passthrough support).

The issue is specific to this loop during identity map initialization
of each device:

domain_context_mapping_one(si_domain, ..., CONTEXT_TT_PASS_THROUGH)
...
		/* Skip top levels of page tables for
		* iommu which has less agaw than default.
		*/
		for (agaw = domain->agaw; agaw != iommu->agaw; agaw--) {
			pgd = phys_to_virt(dma_pte_addr(pgd));
			if (!dma_pte_present(pgd)) {      <------ failing here
				spin_unlock_irqrestore(&iommu->lock, flags);
			return -ENOMEM;
		}

This box has 2 iommu's in it.  The catchall iommu has MGAW == 48, and
SAGAW == 4.  The other iommu has MGAW == 39, SAGAW == 2.

The device that's failing the above pgd test is the only device connected
to the non-catchall iommu, which has a smaller address width than the
domain default.  This test is not necessary since the context is in PT
mode and the ASR is ignored.

Thanks to Don Dutile for discovering and debugging this one.

Cc: stable@kernel.org
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
Chris Wright 2009-12-02 12:06:34 -08:00 committed by David Woodhouse
parent 44cd613c0e
commit 1672af1164
1 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/pci/intel-iommu.c
View File

@ -1530,12 +1530,15 @@ static int domain_context_mapping_one(struct dmar_domain *domain, int segment,
/* Skip top levels of page tables for
* iommu which has less agaw than default.
* Unnecessary for PT mode.
*/
for (agaw = domain->agaw; agaw != iommu->agaw; agaw--) {
pgd = phys_to_virt(dma_pte_addr(pgd));
if (!dma_pte_present(pgd)) {
spin_unlock_irqrestore(&iommu->lock, flags);
return -ENOMEM;
if (translation != CONTEXT_TT_PASS_THROUGH) {
for (agaw = domain->agaw; agaw != iommu->agaw; agaw--) {
pgd = phys_to_virt(dma_pte_addr(pgd));
if (!dma_pte_present(pgd)) {
spin_unlock_irqrestore(&iommu->lock, flags);
return -ENOMEM;
}
}
}
}