[PATCH v3 1/1] powerpc/pseries: fix EEH recovery of some IOV devices

[Sam Bobroff]

EEH recovery currently fails on pSeries for some IOV capable PCI
devices, if CONFIG_PCI_IOV is on and the hypervisor doesn't provide
certain device tree properties for the device. (Found on an IOV
capable device using the ipr driver.)

Recovery fails in pci_enable_resources() at the check on r->parent,
because r->flags is set and r->parent is not.  This state is due to
sriov_init() setting the start, end and flags members of the IOV BARs
but the parent not being set later in
pseries_pci_fixup_iov_resources(), because the
"ibm,open-sriov-vf-bar-info" property is missing.

Correct this by zeroing the resource flags for IOV BARs when they
can't be configured (this is the same method used by sriov_init() and
__pci_read_base()).

VFs cleared this way can't be enabled later, because that requires
another device tree property, "ibm,number-of-configurable-vfs" as well
as support for the RTAS function "ibm_map_pes". These are all part of
hypervisor support for IOV and it seems unlikely that a hypervisor
would ever partially, but not fully, support it. (None are currently
provided by QEMU/KVM.)

Signed-off-by: Sam Bobroff <sbobroff at linux.ibm.com>
---
Hi,

This is a fix to allow EEH recovery to succeed in a specific situation,
which I've tried to explain in the commit message.

As with the RFC version, the IOV BARs are disabled by setting the resource
flags to 0 but the other fields are now left as-is because that is what is done
elsewhere (see sriov_init() and __pci_read_base()).

I've also examined the concern raised by Bjorn Helgaas, that VFs could be
enabled later after the BARs are disabled, and it already seems safe: enabling
VFs (on pseries) depends on another device tree property,
"ibm,number-of-configurable-vfs" as well as support for the RTAS function
"ibm_map_pes". Since these are all part of the hypervisor's support for IOV it
seems unlikely that we would ever see some of them but not all. (None are
currently provided by QEMU/KVM.) (Additionally, the ipr driver on which the EEH
recovery failure was discovered doesn't even seem to have SR-IOV support so it
certainly can't enable VFs.)

Cheers,
Sam.

Patch set v3:
Patch 1/1: powerpc/pseries: fix EEH recovery of some IOV devices
* Moved some useful information from the cover letter to the commit log.

Patch set v2:
Patch 1/1: powerpc/pseries: fix EEH recovery of some IOV devices
* Moved the BAR disabling code to a function.
* Also check in pseries_pci_fixup_resources().

Patch set v1:
Patch 1/1: powerpc/pseries: fix EEH recovery of IOV devices

 arch/powerpc/platforms/pseries/setup.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index b55ad4286dc7..0a9e4243ae1d 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -645,6 +645,15 @@ void of_pci_parse_iov_addrs(struct pci_dev *dev, const int *indexes)
 	}
 }
 
+static void pseries_disable_sriov_resources(struct pci_dev *pdev)
+{
+	int i;
+
+	pci_warn(pdev, "No hypervisor support for SR-IOV on this device, IOV BARs disabled.\n");
+	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++)
+		pdev->resource[i + PCI_IOV_RESOURCES].flags = 0;
+}
+
 static void pseries_pci_fixup_resources(struct pci_dev *pdev)
 {
 	const int *indexes;
@@ -652,10 +661,10 @@ static void pseries_pci_fixup_resources(struct pci_dev *pdev)
 
 	/*Firmware must support open sriov otherwise dont configure*/
 	indexes = of_get_property(dn, "ibm,open-sriov-vf-bar-info", NULL);
-	if (!indexes)
-		return;
-	/* Assign the addresses from device tree*/
-	of_pci_set_vf_bar_size(pdev, indexes);
+	if (indexes)
+		of_pci_set_vf_bar_size(pdev, indexes);
+	else
+		pseries_disable_sriov_resources(pdev);
 }
 
 static void pseries_pci_fixup_iov_resources(struct pci_dev *pdev)
@@ -667,10 +676,10 @@ static void pseries_pci_fixup_iov_resources(struct pci_dev *pdev)
 		return;
 	/*Firmware must support open sriov otherwise dont configure*/
 	indexes = of_get_property(dn, "ibm,open-sriov-vf-bar-info", NULL);
-	if (!indexes)
-		return;
-	/* Assign the addresses from device tree*/
-	of_pci_parse_iov_addrs(pdev, indexes);
+	if (indexes)
+		of_pci_parse_iov_addrs(pdev, indexes);
+	else
+		pseries_disable_sriov_resources(pdev);
 }
 
 static resource_size_t pseries_pci_iov_resource_alignment(struct pci_dev *pdev,
-- 
2.16.1.74.g9b0b1f47b