Messages in this thread | | | Date | Mon, 22 Apr 2013 16:06:45 +0900 | From | Takao Indoh <> | Subject | Re: [PATCH 1/1] intel-iommu: Disable DMA Remapping when intel_iommu=off |
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(2013/04/22 15:50), Wei Hu wrote: > On Sun, Apr 21, 2013 at 10:31 PM, Takao Indoh > <indou.takao@jp.fujitsu.com> wrote: >> (2013/04/20 15:58), Wei Hu wrote: >>> On a VT-d capable machine Linux will enable IOMMU by default. If it >>> then kexec's a second kernel with intel_iommu=off, this second kernel >>> will leave the DMA remapping engine on with no code handling it. The >>> symptom is at least USB and SATA drives stop working. This patch fixes >>> the problem by always disabling DMA remapping when intel_iommu=off. >> >> Even when second kernel boots up with intel_iommu=on, dma-remapping need >> to be disabled as well before it is initialized and enabled again in >> init_dmars(). So, how about something like this? >> >> for_each_drhd_unit(drhd) { >> struct dmar_drhd_unit *drhd; >> if (drhd->ignored) >> continue; >> >> iommu = drhd->iommu; >> if (iommu->gcmd & DMA_GCMD_TE) >> iommu_disable_translation(iommu); >> } >> >> Note, if you agree above code and fix your patch like this, you need >> additinal fix to set iommu->gcmd flag sinse gcmd is always zero here. >> See first hunk of this patch. >> https://lkml.org/lkml/2013/3/20/707 > > Thanks for your reply. I reviewed your patch. Are you suggesting > keeping your change to dmar.c, and moving your change to intel-iommu.c > (i.e. the code you just showed) up after the call to > dmar_table_init()? >
Yes, exactly.
Thanks, Takao Indoh
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