From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takao Indoh Subject: Re: [PATCH 1/1] intel-iommu: Disable DMA Remapping when intel_iommu=off Date: Mon, 22 Apr 2013 14:31:18 +0900 Message-ID: <5174CB26.9060908@jp.fujitsu.com> References: <1366441080-5937-1-git-send-email-wei@aristanetworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1366441080-5937-1-git-send-email-wei-BGArkANP9klv6pq1l3V1OdBPR1lH4CV8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: wei-BGArkANP9klv6pq1l3V1OdBPR1lH4CV8@public.gmane.org Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: iommu@lists.linux-foundation.org (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, Takao Indoh > > Signed-off-by: Wei Hu > --- > drivers/iommu/intel-iommu.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 0099667..0b8f8bb 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -3681,8 +3681,12 @@ int __init intel_iommu_init(void) > return -ENODEV; > } > > - if (no_iommu || dmar_disabled) > + if (no_iommu || dmar_disabled) { > + struct dmar_drhd_unit *drhd; > + for_each_drhd_unit(drhd) > + iommu_disable_translation(drhd->iommu); > return -ENODEV; > + } > > if (iommu_init_mempool()) { > if (force_on) >