Messages in this thread | | | Date | Thu, 30 Apr 2009 16:37:52 -0700 | From | Randy Dunlap <> | Subject | Re: [PATCH] Intel IOMMU Pass Through Support |
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Andrew Morton wrote: > On Wed, 15 Apr 2009 17:19:57 -0700 > Fenghua Yu <fenghua.yu@intel.com> wrote: > >> The patch adds kernel parameter intel_iommu=pt to set up pass through mode in >> context mapping entry. This disables DMAR in linux kernel; but KVM still runs on >> VT-d and interrupt remapping still works. >> >> In this mode, kernel uses swiotlb for DMA API functions but other VT-d >> functionalities are enabled for KVM. KVM always uses multi level translation >> page table in VT-d. By default, pass though mode is disabled in kernel. >> >> This is useful when people don't want to enable VT-d DMAR in kernel but still >> want to use KVM and interrupt remapping for reasons like DMAR performance >> concern or debug purpose. >> > > The patch is now in linux-next and broke my build. > > arch/x86/built-in.o: In function `iommu_setup': > arch/x86/kernel/pci-dma.c:215: undefined reference to `iommu_pass_through' > arch/x86/built-in.o: In function `pci_swiotlb_init': > arch/x86/kernel/pci-swiotlb.c:74: undefined reference to `iommu_pass_through' > > Because iommu_pass_through is defined in drivers/pci/intel-iommu.c and > > # CONFIG_DMAR is not set > > I'll need to cook up some local hack to work around that. >
Patch just went to linux-next mailing list (but should have also gone to lkml):
http://marc.info/?l=linux-next&m=124113213400748&w=2
> > Also, the patch in linux-next (but not the one which I'm replying to > here does: > > : --- a/arch/x86/kernel/pci-dma.c > : +++ b/arch/x86/kernel/pci-dma.c > : @@ -160,6 +160,8 @@ again: > : return page_address(page); > : } > : > : +extern int iommu_pass_through; > : + > > Which is wrong and unnecessary - the variable was already declared in a > header file. > > scripts/checkpatch.pl would have warned you about this error, but > apparently neither you nor the people who reviewed or merged the patch > bother to use it.
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