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Date: Thu, 30 Apr 2009 17:05:10 -0700 From: Fenghua Yu <fenghua.yu@...el.com> To: Andrew Morton <akpm@...ux-foundation.org>, Randy Dunlap <rdunlap@...otime.net> Cc: "Yu, Fenghua" <fenghua.yu@...el.com>, "dwmw2@...radead.org" <dwmw2@...radead.org>, "mingo@...e.hu" <mingo@...e.hu>, "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>, "Han, Weidong" <weidong.han@...el.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org> Subject: Re: [PATCH] Intel IOMMU Pass Through Support On Thu, Apr 30, 2009 at 04:37:52PM -0700, Randy Dunlap wrote: > Andrew Morton wrote: > > On Wed, 15 Apr 2009 17:19:57 -0700 > > Fenghua Yu <fenghua.yu@...el.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 That's right. I just posted this patch to fix the compiling errors. > > > > > > 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. Actually checkpatch.pl doesn't report anything wrong with this statement. The following patch removes this statement on the top of linux-next. Signed-off-by: Fenghua Yu <fenghua.yu@...el.com> --- pci-dma.c | 2 -- 1 files changed, 2 deletions(-) diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 8cad0d8..049005e 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -160,8 +162,6 @@ again: return page_address(page); } -extern int iommu_pass_through; - /* * See <Documentation/x86_64/boot-options.txt> for the iommu kernel parameter * documentation. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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