iommu/fsl: Enable default DMA window for PCIe devices once detached from domain.

Once the PCIe device assigned to a guest VM (via VFIO) gets detached from the iommu domain
(when guest terminates), its PAMU table entry is disabled. So, this would prevent the device
from being used once it's assigned back to the host.

This patch allows for creation of a default DMA window corresponding to the device
and subsequently enabling the PAMU table entry. Before we enable the entry, we ensure that
the device's bus master capability is disabled (device quiesced).

Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
Change-Id: Iab4da4adfac8536a6834011431a395ba3a4982d2
Reviewed-on: http://git.am.freescale.net:8181/10257
Tested-by: Review Code-CDREVIEW <CDREVIEW@freescale.com>
Reviewed-by: Stuart Yoder <stuart.yoder@freescale.com>
Reviewed-by: Jose Rivera <German.Rivera@freescale.com>

1 files changed, 49 insertions, 3 deletions

diff --git a/drivers/iommu/fsl_pamu_domain.c b/drivers/iommu/fsl_pamu_domain.c
index 844997e..e62048b 100644
--- a/drivers/iommu/fsl_pamu_domain.c
+++ b/drivers/iommu/fsl_pamu_domain.c
@@ -366,17 +366,63 @@ static inline struct device_domain_info *find_domain(struct device *dev)
 	return dev->archdata.iommu_domain;
 }
 
+/* Disable device DMA capability and enable default DMA window */
+static void disable_device_dma(struct device_domain_info *info,
+				int enable_dma_window)
+{
+#ifdef CONFIG_PCI
+	if (info->dev->bus == &pci_bus_type) {
+		struct pci_dev *pdev = NULL;
+		u16 pci_command;
+
+		pdev = to_pci_dev(info->dev);
+		pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
+		/* disable device bus master capability */
+		if (pci_command & PCI_COMMAND_MASTER) {
+			pci_command &= ~PCI_COMMAND_MASTER;
+			pci_write_config_word(pdev, PCI_COMMAND, pci_command);
+		}
+	}
+#endif
+
+	if (enable_dma_window)
+		enable_default_dma_window(info->liodn);
+}
+
+static int check_for_shared_liodn(struct device_domain_info *info)
+{
+	struct device_domain_info *tmp;
+
+	/*
+	 * Sanity check, to ensure that this is not a
+	 * shared LIODN. In case of a PCIe controller
+	 * it's possible that all PCIe devices share
+	 * the same LIODN.
+	 */
+	list_for_each_entry(tmp, &info->domain->devices, link) {
+		if (info->liodn == tmp->liodn)
+			return 1;
+	}
+
+	return 0;
+}
+
 static void remove_device_ref(struct device_domain_info *info, u32 win_cnt)
 {
 	unsigned long flags;
+	int enable_dma_window = 0;
 
 	list_del(&info->link);
 	spin_lock_irqsave(&iommu_lock, flags);
-	if (win_cnt > 1)
-		pamu_free_subwins(info->liodn);
-	pamu_disable_liodn(info->liodn);
+	if (!check_for_shared_liodn(info)) {
+		if (win_cnt > 1)
+			pamu_free_subwins(info->liodn);
+		pamu_disable_liodn(info->liodn);
+		enable_dma_window = 1;
+	}
 	spin_unlock_irqrestore(&iommu_lock, flags);
 	spin_lock_irqsave(&device_domain_lock, flags);
+	disable_device_dma(info, enable_dma_window);
 	info->dev->archdata.iommu_domain = NULL;
 	kmem_cache_free(iommu_devinfo_cache, info);
 	spin_unlock_irqrestore(&device_domain_lock, flags);