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

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Date:   Thu, 2 Sep 2021 09:46:25 -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,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH v4] iommu/of: Fix pci_request_acs() before enumerating
 PCI devices

[+cc Marek, Anders, Robin]

On Fri, Aug 20, 2021 at 02:57:12PM -0500, Bjorn Helgaas wrote:
> 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!

I dropped this for now, until the problems reported by Marek and
Anders get sorted out.

> > ---
> >  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
> >