Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752906AbdHIIeX (ORCPT ); Wed, 9 Aug 2017 04:34:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46836 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752569AbdHIIeV (ORCPT ); Wed, 9 Aug 2017 04:34:21 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com E0B13A70A Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=bhe@redhat.com From: Baoquan He To: jroedel@suse.de Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Baoquan He Subject: [PATCH v10 10/12] iommu/amd: Allocate memory below 4G for dev table if translation pre-enabled Date: Wed, 9 Aug 2017 16:33:42 +0800 Message-Id: <1502267624-7066-11-git-send-email-bhe@redhat.com> In-Reply-To: <1502267624-7066-1-git-send-email-bhe@redhat.com> References: <1502267624-7066-1-git-send-email-bhe@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Wed, 09 Aug 2017 08:34:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2014 Lines: 53 AMD pointed out it's unsafe to update the device-table while iommu is enabled. It turns out that device-table pointer update is split up into two 32bit writes in the IOMMU hardware. So updating it while the IOMMU is enabled could have some nasty side effects. The safe way to work around this is to always allocate the device-table below 4G, including the old device-table in normal kernel and the device-table used for copying the content of the old device-table in kdump kernel. Meanwhile we need check if the address of old device-table is above 4G because it might has been touched accidentally in corrupted 1st kernel. Signed-off-by: Baoquan He --- v9->v10: The judgement of the address of old_devtb_phys should be '>= 0x100000000ULL'. drivers/iommu/amd_iommu_init.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c index d08ad74b0928..c348732f27d7 100644 --- a/drivers/iommu/amd_iommu_init.c +++ b/drivers/iommu/amd_iommu_init.c @@ -885,11 +885,15 @@ static bool copy_device_table(void) } old_devtb_phys = entry & PAGE_MASK; + if (old_devtb_phys >= 0x100000000ULL) { + pr_err("The address of old device table is above 4G, not trustworthy!/n"); + return false; + } old_devtb = memremap(old_devtb_phys, dev_table_size, MEMREMAP_WB); if (!old_devtb) return false; - gfp_flag = GFP_KERNEL | __GFP_ZERO; + gfp_flag = GFP_KERNEL | __GFP_ZERO | GFP_DMA32; old_dev_tbl_cpy = (void *)__get_free_pages(gfp_flag, get_order(dev_table_size)); if (old_dev_tbl_cpy == NULL) { @@ -2432,7 +2436,8 @@ static int __init early_amd_iommu_init(void) /* Device table - directly used by all IOMMUs */ ret = -ENOMEM; - amd_iommu_dev_table = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, + amd_iommu_dev_table = (void *)__get_free_pages( + GFP_KERNEL | __GFP_ZERO | GFP_DMA32, get_order(dev_table_size)); if (amd_iommu_dev_table == NULL) goto out; -- 2.5.5