Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753360Ab3DVGvi (ORCPT ); Mon, 22 Apr 2013 02:51:38 -0400 Received: from mail-oa0-f50.google.com ([209.85.219.50]:32858 "EHLO mail-oa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752640Ab3DVGvh (ORCPT ); Mon, 22 Apr 2013 02:51:37 -0400 MIME-Version: 1.0 In-Reply-To: <5174CB26.9060908@jp.fujitsu.com> References: <1366441080-5937-1-git-send-email-wei@aristanetworks.com> <5174CB26.9060908@jp.fujitsu.com> From: Wei Hu Date: Sun, 21 Apr 2013 23:50:56 -0700 Message-ID: Subject: Re: [PATCH 1/1] intel-iommu: Disable DMA Remapping when intel_iommu=off To: Takao Indoh Cc: dwmw2@infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1668 Lines: 37 On Sun, Apr 21, 2013 at 10:31 PM, Takao Indoh 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()? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/