linux-kernel - [PATCH] intel-iommu: Quiesce devices before disabling IOMMU

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Message-Id: <1377069354-5056-1-git-send-email-indou.takao@jp.fujitsu.com>
Date:	Wed, 21 Aug 2013 16:15:54 +0900
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
	dwmw2@...radead.org, joro@...tes.org
Cc:	kexec@...ts.infradead.org, alex.williamson@...hat.com
Subject: [PATCH] intel-iommu: Quiesce devices before disabling IOMMU

This patch quiesces devices before disabling IOMMU on boot to stop
ongoing DMA. In intel_iommu_init(), check context entries and if there
is entry whose present bit is set then reset corresponding device.

When IOMMU is already enabled on boot, it is disabled and new DMAR table
is created and then re-enabled in intel_iommu_init(). This causes DMAR
faults if there are in-flight DMAs.

This causes problem on kdump. Devices are working in first kernel, and
after switching to second kernel and initializing IOMMU, many DMAR faults
occur and it causes problems like driver error or PCI SERR, at last
kdump fails. This patch fixes this problem.

Signed-off-by: Takao Indoh <indou.takao@...fujitsu.com>


NOTE:
To reset devices this patch uses bus reset interface introduced by
following commits in PCI "next" branch.

64e8674fbe6bc848333a9b7e19f8cc019dde9eab
5c32b35b004f5ef70dcf62bbc42b8bed1e50b471
2e35afaefe64946caaecfacaf7fb568e46185e88
608c388122c72e1bf11ba8113434eb3d0c40c32d
77cb985ad4acbe66a92ead1bb826deffa47dd33f
090a3c5322e900f468b3205b76d0837003ad57b2
a6cbaadea0af9b4aa6eee2882f2aa761ab91a4f8
de0c548c33429cc78fd47a3c190c6d00b0e4e441
1b95ce8fc9c12fdb60047f2f9950f29e76e7c66d
---
 drivers/iommu/intel-iommu.c |   55 ++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 54 insertions(+), 1 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index eec0d3e..efb98eb 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3663,6 +3663,56 @@ static struct notifier_block device_nb = {
 	.notifier_call = device_notifier,
 };
 
+/* Reset PCI devices if its entry exists in DMAR table */
+static void __init iommu_reset_devices(struct intel_iommu *iommu, u16 segment)
+{
+	u64 addr;
+	struct root_entry *root;
+	struct context_entry *context;
+	int bus, devfn;
+	struct pci_dev *dev;
+
+	addr = dmar_readq(iommu->reg + DMAR_RTADDR_REG);
+	if (!addr)
+		return;
+
+	/*
+	 *  In the case of kdump, ioremap is needed because root-entry table
+	 *  exists in first kernel's memory area which is not mapped in second
+	 *  kernel
+	 */
+	root = (struct root_entry *)ioremap(addr, PAGE_SIZE);
+	if (!root)
+		return;
+
+	for (bus = 0; bus < ROOT_ENTRY_NR; bus++) {
+		if (!root_present(&root[bus]))
+			continue;
+
+		context = (struct context_entry *)ioremap(
+			root[bus].val & VTD_PAGE_MASK, PAGE_SIZE);
+		if (!context)
+			continue;
+
+		for (devfn = 0; devfn < ROOT_ENTRY_NR; devfn++) {
+			if (!context_present(&context[devfn]))
+				continue;
+
+			dev = pci_get_domain_bus_and_slot(segment, bus, devfn);
+			if (!dev)
+				continue;
+
+			if (!pci_reset_bus(dev->bus)) /* go to next bus */
+				break;
+			else /* Try per-function reset */
+				pci_reset_function(dev);
+
+		}
+		iounmap(context);
+	}
+	iounmap(root);
+}
+
 int __init intel_iommu_init(void)
 {
 	int ret = 0;
@@ -3687,8 +3737,11 @@ int __init intel_iommu_init(void)
 			continue;
 
 		iommu = drhd->iommu;
-		if (iommu->gcmd & DMA_GCMD_TE)
+		if (iommu->gcmd & DMA_GCMD_TE) {
+			if (reset_devices)
+				iommu_reset_devices(iommu, drhd->segment);
 			iommu_disable_translation(iommu);
+		}
 	}
 
 	if (dmar_dev_scope_init() < 0) {
-- 
1.7.1


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