From 1672af1164d3d50ba8908014fd34cc0b58afdc1e Mon Sep 17 00:00:00 2001 From: Chris Wright Date: Wed, 2 Dec 2009 12:06:34 -0800 Subject: 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 19943b0e30b05d42e494ae6fef78156ebc8c637e "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 Signed-off-by: David Woodhouse --- drivers/pci/intel-iommu.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'drivers/pci') diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c index e3e84cac0e9..46607953533 100644 --- a/drivers/pci/intel-iommu.c +++ b/drivers/pci/intel-iommu.c @@ -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; + } } } } -- cgit v1.2.3-70-g09d2