[PATCH v3] iommu/of: Fix pci_request_acs() before enumerating PCI devices

[PATCH v3] iommu/of: Fix pci_request_acs() before enumerating PCI devices

[Wang Xingang]

From: Xingang Wang <wangxingang5@huawei.com>

When booting with devicetree, the pci_request_acs() is called after the
enumeration and initialization of PCI devices, thus the ACS is not
enabled. And ACS should be enabled when IOMMU is detected for the
PCI host bridge, so add check for IOMMU before probe of PCI host and call
pci_request_acs() to make sure ACS will be enabled when enumerating PCI
devices.

Fixes: 6bf6c24720d33 ("iommu/of: Request ACS from the PCI core when
configuring IOMMU linkage")
Signed-off-by: Xingang Wang <wangxingang5@huawei.com>
---
 drivers/iommu/of_iommu.c                 |  1 -
 drivers/pci/controller/pci-host-common.c | 17 +++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index a9d2df001149..54a14da242cc 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 {
diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
index d3924a44db02..5904ad0bd9ae 100644
--- a/drivers/pci/controller/pci-host-common.c
+++ b/drivers/pci/controller/pci-host-common.c
@@ -49,6 +49,21 @@ static struct pci_config_window *gen_pci_init(struct device *dev,
 	return cfg;
 }
 
+static void pci_host_enable_acs(struct pci_host_bridge *bridge)
+{
+	struct device_node *np = bridge->dev.parent->of_node;
+	static bool acs_enabled;
+
+	if (!np || acs_enabled)
+		return;
+
+	/* Detect IOMMU and make sure ACS will be enabled */
+	if (of_property_read_bool(np, "iommu-map")) {
+		acs_enabled = true;
+		pci_request_acs();
+	}
+}
+
 int pci_host_common_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -81,6 +96,8 @@ int pci_host_common_probe(struct platform_device *pdev)
 	bridge->ops = (struct pci_ops *)&ops->pci_ops;
 	bridge->msi_domain = true;
 
+	pci_host_enable_acs(bridge);
+
 	return pci_host_probe(bridge);
 }
 EXPORT_SYMBOL_GPL(pci_host_common_probe);
-- 
2.19.1

Re: [PATCH v3] iommu/of: Fix pci_request_acs() before enumerating PCI devices

[Rob Herring]

On Thu, May 20, 2021 at 2:28 AM Wang Xingang <wangxingang5@huawei.com> wrote:
>
> From: Xingang Wang <wangxingang5@huawei.com>
>
> When booting with devicetree, the pci_request_acs() is called after the
> enumeration and initialization of PCI devices, thus the ACS is not
> enabled. And ACS should be enabled when IOMMU is detected for the
> PCI host bridge, so add check for IOMMU before probe of PCI host and call
> pci_request_acs() to make sure ACS will be enabled when enumerating PCI
> devices.
>
> Fixes: 6bf6c24720d33 ("iommu/of: Request ACS from the PCI core when
> configuring IOMMU linkage")
> Signed-off-by: Xingang Wang <wangxingang5@huawei.com>
> ---
>  drivers/iommu/of_iommu.c                 |  1 -
>  drivers/pci/controller/pci-host-common.c | 17 +++++++++++++++++
>  2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index a9d2df001149..54a14da242cc 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 {
> diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
> index d3924a44db02..5904ad0bd9ae 100644
> --- a/drivers/pci/controller/pci-host-common.c
> +++ b/drivers/pci/controller/pci-host-common.c

This file is generally only for ECAM compliant hosts. Are those the
only hosts we need to support this? From the looks of dts files with
iommu-map, that would be dropping support in lots of cases.

Perhaps in devm_of_pci_bridge_init() or one of the functions it calls
is the better place.

> @@ -49,6 +49,21 @@ static struct pci_config_window *gen_pci_init(struct device *dev,
>         return cfg;
>  }
>
> +static void pci_host_enable_acs(struct pci_host_bridge *bridge)
> +{
> +       struct device_node *np = bridge->dev.parent->of_node;
> +       static bool acs_enabled;
> +
> +       if (!np || acs_enabled)
> +               return;
> +
> +       /* Detect IOMMU and make sure ACS will be enabled */
> +       if (of_property_read_bool(np, "iommu-map")) {
> +               acs_enabled = true;
> +               pci_request_acs();

Given this function just sets a variable, I don't think you need the
static acs_enabled here.

> +       }
> +}
> +
>  int pci_host_common_probe(struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
> @@ -81,6 +96,8 @@ int pci_host_common_probe(struct platform_device *pdev)
>         bridge->ops = (struct pci_ops *)&ops->pci_ops;
>         bridge->msi_domain = true;
>
> +       pci_host_enable_acs(bridge);
> +
>         return pci_host_probe(bridge);
>  }
>  EXPORT_SYMBOL_GPL(pci_host_common_probe);
> --
> 2.19.1
>