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

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Date:   Fri, 20 Aug 2021 14:57:12 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Wang Xingang <wangxingang5@...wei.com>
Cc:     robh@...nel.org, will@...nel.org, joro@...tes.org,
        robh+dt@...nel.org, gregkh@...uxfoundation.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, xieyingtai@...wei.com
Subject: Re: [PATCH v4] iommu/of: Fix pci_request_acs() before enumerating
 PCI devices

On Fri, May 21, 2021 at 03:03:24AM +0000, Wang Xingang 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>

Applied to pci/virtualization for v5.15, thanks!

> ---
>  drivers/iommu/of_iommu.c | 1 -
>  drivers/pci/of.c         | 8 +++++++-
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> 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
>