[PATCH v2] PCI : Fix pcie_flag_reg in set_pcie_port_type

[PATCH v2] PCI : Fix pcie_flag_reg in set_pcie_port_type

[Gowthami Thiagarajan]

When an invalid PCIe topology is detected, the set_pcie_port_type function 
does not set the port type correctly. This issue can occur in 
configurations such as:

	Root Port ---> Downstream Port ---> Root Port

In such cases, the topology is identified as invalid and due to the incorrect 
port type setting, the extended configuration space of the child device becomes 
inaccessible.

Signed-off-by: Gowthami Thiagarajan <gthiagarajan@marvell.com>
---
v1->v2:
	Updated commit description

 drivers/pci/probe.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 4f68414c3086..263ec21451d9 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1596,7 +1596,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
 		if (pcie_downstream_port(parent)) {
 			pci_info(pdev, "claims to be downstream port but is acting as upstream port, correcting type\n");
 			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
-			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM;
+			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM << 4;
 		}
 	} else if (type == PCI_EXP_TYPE_UPSTREAM) {
 		/*
@@ -1607,7 +1607,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
 		if (pci_pcie_type(parent) == PCI_EXP_TYPE_UPSTREAM) {
 			pci_info(pdev, "claims to be upstream port but is acting as downstream port, correcting type\n");
 			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
-			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM;
+			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM << 4;
 		}
 	}
 }
-- 
2.25.1

Re: [PATCH v2] PCI : Fix pcie_flag_reg in set_pcie_port_type

[Bjorn Helgaas]

[+cc Mika, Andy]

On Fri, Dec 13, 2024 at 12:32:41PM +0530, Gowthami Thiagarajan wrote:
> When an invalid PCIe topology is detected, the set_pcie_port_type function 
> does not set the port type correctly. This issue can occur in 
> configurations such as:
> 
> 	Root Port ---> Downstream Port ---> Root Port
> 
> In such cases, the topology is identified as invalid and due to the
> incorrect port type setting, the extended configuration space of the
> child device becomes inaccessible.

From reading the code, it looks like the underlying problem is
components that advertise the wrong PCIe Device/Port Type.

set_pcie_port_type() already detects that incorrect Port Type and
tries to correct it, but it puts the corrected type in bits [3:0]
instead of [7:4] where it belongs.

This looks like a bug from ca78410403dd ("PCI: Get rid of
dev->has_secondary_link flag").  If so, we should add a Fixes: tag for
that and possibly a stable tag.

This looks like a clear bug.  What system tripped over this?  It's
useful to have bread crumbs like that in case we see other issues
caused by hardware/firmware defects like this.

> Signed-off-by: Gowthami Thiagarajan <gthiagarajan@marvell.com>
> ---
> v1->v2:
> 	Updated commit description
> 
>  drivers/pci/probe.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 4f68414c3086..263ec21451d9 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1596,7 +1596,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
>  		if (pcie_downstream_port(parent)) {
>  			pci_info(pdev, "claims to be downstream port but is acting as upstream port, correcting type\n");
>  			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
> -			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM;
> +			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM << 4;
>  		}
>  	} else if (type == PCI_EXP_TYPE_UPSTREAM) {
>  		/*
> @@ -1607,7 +1607,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
>  		if (pci_pcie_type(parent) == PCI_EXP_TYPE_UPSTREAM) {
>  			pci_info(pdev, "claims to be upstream port but is acting as downstream port, correcting type\n");
>  			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
> -			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM;
> +			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM << 4;
>  		}
>  	}
>  }
> -- 
> 2.25.1
> 

Re: [PATCH v2] PCI : Fix pcie_flag_reg in set_pcie_port_type

[Mika Westerberg]

On Fri, Dec 13, 2024 at 12:47:00PM -0600, Bjorn Helgaas wrote:
> [+cc Mika, Andy]
> 
> On Fri, Dec 13, 2024 at 12:32:41PM +0530, Gowthami Thiagarajan wrote:
> > When an invalid PCIe topology is detected, the set_pcie_port_type function 
> > does not set the port type correctly. This issue can occur in 
> > configurations such as:
> > 
> > 	Root Port ---> Downstream Port ---> Root Port
> > 
> > In such cases, the topology is identified as invalid and due to the
> > incorrect port type setting, the extended configuration space of the
> > child device becomes inaccessible.
> 
> >From reading the code, it looks like the underlying problem is
> components that advertise the wrong PCIe Device/Port Type.
> 
> set_pcie_port_type() already detects that incorrect Port Type and
> tries to correct it, but it puts the corrected type in bits [3:0]
> instead of [7:4] where it belongs.
> 
> This looks like a bug from ca78410403dd ("PCI: Get rid of
> dev->has_secondary_link flag").  If so, we should add a Fixes: tag for
> that and possibly a stable tag.

Yeah agree, this is definitely a bug in that commit.

> This looks like a clear bug.  What system tripped over this?  It's
> useful to have bread crumbs like that in case we see other issues
> caused by hardware/firmware defects like this.
> 
> > Signed-off-by: Gowthami Thiagarajan <gthiagarajan@marvell.com>
> > ---
> > v1->v2:
> > 	Updated commit description
> > 
> >  drivers/pci/probe.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 4f68414c3086..263ec21451d9 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -1596,7 +1596,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
> >  		if (pcie_downstream_port(parent)) {
> >  			pci_info(pdev, "claims to be downstream port but is acting as upstream port, correcting type\n");
> >  			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
> > -			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM;
> > +			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM << 4;
> >  		}
> >  	} else if (type == PCI_EXP_TYPE_UPSTREAM) {
> >  		/*
> > @@ -1607,7 +1607,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
> >  		if (pci_pcie_type(parent) == PCI_EXP_TYPE_UPSTREAM) {
> >  			pci_info(pdev, "claims to be upstream port but is acting as downstream port, correcting type\n");
> >  			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
> > -			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM;
> > +			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM << 4;
> >  		}
> >  	}
> >  }
> > -- 
> > 2.25.1
> > 

Re: [PATCH v2] PCI : Fix pcie_flag_reg in set_pcie_port_type

[Ilpo Järvinen]

On Fri, 13 Dec 2024, Gowthami Thiagarajan wrote:

> When an invalid PCIe topology is detected, the set_pcie_port_type function 
> does not set the port type correctly. This issue can occur in 
> configurations such as:
> 
> 	Root Port ---> Downstream Port ---> Root Port
> 
> In such cases, the topology is identified as invalid and due to the incorrect 
> port type setting, the extended configuration space of the child device becomes 
> inaccessible.
> 
> Signed-off-by: Gowthami Thiagarajan <gthiagarajan@marvell.com>
> ---
> v1->v2:
> 	Updated commit description
> 
>  drivers/pci/probe.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 4f68414c3086..263ec21451d9 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1596,7 +1596,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
>  		if (pcie_downstream_port(parent)) {
>  			pci_info(pdev, "claims to be downstream port but is acting as upstream port, correcting type\n");
>  			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
> -			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM;
> +			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM << 4;

Use FIELD_PREP() please.

-- 
 i.

>  		}
>  	} else if (type == PCI_EXP_TYPE_UPSTREAM) {
>  		/*
> @@ -1607,7 +1607,7 @@ void set_pcie_port_type(struct pci_dev *pdev)
>  		if (pci_pcie_type(parent) == PCI_EXP_TYPE_UPSTREAM) {
>  			pci_info(pdev, "claims to be upstream port but is acting as downstream port, correcting type\n");
>  			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
> -			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM;
> +			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM << 4;
>  		}
>  	}
>  }
>