linux-kernel - [PATCH 1/1] iommu/of: Fix request and enable ACS for of_iommu

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Date:   Fri, 7 May 2021 12:49:53 +0000
From:   Wang Xingang <wangxingang5@...wei.com>
To:     <will@...nel.org>, <joro@...tes.org>
CC:     <bhelgaas@...gle.com>, <gregkh@...uxfoundation.org>,
        <iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <xieyingtai@...wei.com>,
        <wangxingang5@...wei.com>
Subject: [PATCH 1/1] iommu/of: Fix request and enable ACS for of_iommu_configure

From: Xingang Wang <wangxingang5@...wei.com>

When request ACS for PCI device in of_iommu_configure, the pci device
has already been scanned and added with 'pci_acs_enable=0'. So the
pci_request_acs() in current procedure does not work for enabling ACS.
Besides, the ACS should be enabled only if there's an IOMMU in system.
So this fix the call of pci_request_acs() and call pci_enable_acs() to
make sure ACS is enabled for the pci_device.

Fixes: 6bf6c24720d33 ("iommu/of: Request ACS from the PCI core when
configuring IOMMU linkage")
Signed-off-by: Xingang Wang <wangxingang5@...wei.com>
---
 drivers/iommu/of_iommu.c | 10 +++++++++-
 drivers/pci/pci.c        |  2 +-
 include/linux/pci.h      |  1 +
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index a9d2df001149..dc621861ae72 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -205,7 +205,6 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 			.np = master_np,
 		};
 
-		pci_request_acs();
 		err = pci_for_each_dma_alias(to_pci_dev(dev),
 					     of_pci_iommu_init, &info);
 	} else {
@@ -222,6 +221,15 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
 		/* The fwspec pointer changed, read it again */
 		fwspec = dev_iommu_fwspec_get(dev);
 		ops    = fwspec->ops;
+
+		/*
+		 * If we found an IOMMU and the device is pci,
+		 * make sure we enable ACS.
+		 */
+		if (dev_is_pci(dev)) {
+			pci_request_acs();
+			pci_enable_acs(to_pci_dev(dev));
+		}
 	}
 	/*
 	 * If we have reason to believe the IOMMU driver missed the initial
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b717680377a9..4e4f98ee2870 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -926,7 +926,7 @@ static void pci_std_enable_acs(struct pci_dev *dev)
  * pci_enable_acs - enable ACS if hardware support it
  * @dev: the PCI device
  */
-static void pci_enable_acs(struct pci_dev *dev)
+void pci_enable_acs(struct pci_dev *dev)
 {
 	if (!pci_acs_enable)
 		goto disable_acs_redir;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c20211e59a57..e6a8bfbc9c98 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2223,6 +2223,7 @@ static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
 }
 
 void pci_request_acs(void);
+void pci_enable_acs(struct pci_dev *dev);
 bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags);
 bool pci_acs_path_enabled(struct pci_dev *start,
 			  struct pci_dev *end, u16 acs_flags);
-- 
2.19.1