From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugme-daemon@bugzilla.kernel.org
Subject: [Bug 12222] kernel BUG at drivers/pci/intel-iommu.c:1373!
Date: Mon, 15 Dec 2008 13:40:07 -0800 (PST)
Message-ID: <20081215214007.0C058108041@picon.linux-foundation.org>
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http://bugzilla.kernel.org/show_bug.cgi?id=12222
------- Comment #4 from grundler@parisc-linux.org 2008-12-15 13:40 -------
In 2.6.28-rc8 kernel, the BUG_ON is now at line 1276.
The BUG_ON is just indicating the IOMMU page table entry is already (or still)
in use.
My guess is either the IOMMU space allocator is buggy *OR* the unmap code isn't
clearing dma_pte_addr() (off by one?). Perhaps there needs to be a wmb() in
intel_unmap_sg() between dma_pte_clear_range() and the later __free_iova()
call.
intel_iommu=off means no IOMMU will be used. For normal workloads with modern
PCIe devices (which are all 64-bit, right?), there would be no perf impact. Not
until you wanted to get better isolation for virtual guest OSs or used a device
driver that only offers 32-bit DMA support, will it matter.
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