linux-kernel - Re: [PATCH v4] iommu/of: Fix pci_request_acs() before enumerating PCI devices

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Date:   Fri, 21 May 2021 14:03:23 -0500
From:   Rob Herring <robh@...nel.org>
To:     Wang Xingang <wangxingang5@...wei.com>
Cc:     Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux IOMMU <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        PCI <linux-pci@...r.kernel.org>, xieyingtai@...wei.com
Subject: Re: [PATCH v4] iommu/of: Fix pci_request_acs() before enumerating PCI devices

On Thu, May 20, 2021 at 10:03 PM Wang Xingang <wangxingang5@...wei.com> wrote:
>
> From: Xingang Wang <wangxingang5@...wei.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@...wei.com>
> ---
>  drivers/iommu/of_iommu.c | 1 -
>  drivers/pci/of.c         | 8 +++++++-
>  2 files changed, 7 insertions(+), 2 deletions(-)

Reviewed-by: Rob Herring <robh@...nel.org>

> 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/of.c b/drivers/pci/of.c
> index da5b414d585a..2313c3f848b0 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -581,9 +581,15 @@ static int pci_parse_request_of_pci_ranges(struct device *dev,
>
>  int devm_of_pci_bridge_init(struct device *dev, struct pci_host_bridge *bridge)
>  {
> -       if (!dev->of_node)
> +       struct device_node *node = dev->of_node;
> +
> +       if (!node)
>                 return 0;
>
> +       /* Detect IOMMU and make sure ACS will be enabled */
> +       if (of_property_read_bool(node, "iommu-map"))
> +               pci_request_acs();
> +
>         bridge->swizzle_irq = pci_common_swizzle;
>         bridge->map_irq = of_irq_parse_and_map_pci;
>
> --
> 2.19.1
>