On 27/09/2019 03:15, Frederic Barrat wrote:

Le 26/09/2019 à 18:44, Andrew Donnellan a écrit :

quoted

On 9/9/19 5:45 pm, Frederic Barrat wrote:

quoted

Taking a reference on the pci_dev structure was required with initial
commit 184cd4a3b962 ("powerpc/powernv: PCI support for p7IOC under
OPAL v2"), where we were storing the pci_dev in the pci_dn structure.

However, the pci_dev was later removed from the pci_dn structure, but
the reference was kept. See commit 902bdc57451c ("powerpc/powernv/idoa:
Remove unnecessary pcidev from pci_dn").

The pnv_ioda_pe structure life cycle is the same as the pci_dev
structure, the PE is freed when the device is released. So we don't
need a reference for the pci_dev stored in the PE, otherwise the
pci_dev will never be released. Which is not really a surprise as the
comment (removed here as no longer needed) was stating as much.

Fixes: 902bdc57451c ("powerpc/powernv/idoa: Remove unnecessary pcidev from pci_dn")
Signed-off-by: Frederic Barrat <redacted>
---
  arch/powerpc/platforms/powernv/pci-ioda.c | 11 +----------
  1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index d8080558d020..92767f006f20 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c

@@ -1062,14 +1062,6 @@ static struct pnv_ioda_pe *pnv_ioda_setup_dev_PE(struct pci_dev *dev)

          return NULL;
      }
-    /* NOTE: We get only one ref to the pci_dev for the pdn, not for the
-     * pointer in the PE data structure, both should be destroyed at the
-     * same time. However, this needs to be looked at more closely again
-     * once we actually start removing things (Hotplug, SR-IOV, ...)
-     *
-     * At some point we want to remove the PDN completely anyways
-     */
-    pci_dev_get(dev);
      pdn->pe_number = pe->pe_number;
      pe->flags = PNV_IODA_PE_DEV;
      pe->pdev = dev;

@@ -1084,7 +1076,6 @@ static struct pnv_ioda_pe *pnv_ioda_setup_dev_PE(struct pci_dev *dev)

          pnv_ioda_free_pe(pe);
          pdn->pe_number = IODA_INVALID_PE;
          pe->pdev = NULL;
-        pci_dev_put(dev);
          return NULL;
      }

@@ -1228,7 +1219,7 @@ static struct pnv_ioda_pe *pnv_ioda_setup_npu_PE(struct pci_dev *npu_pdev)

               */
              dev_info(&npu_pdev->dev,
                  "Associating to existing PE %x\n", pe_num);
-            pci_dev_get(npu_pdev);
+            pci_dev_get(npu_pdev); // still needed after 902bdc57451c ?

Did you mean to leave that comment in?

Yes, I assumed the series wouldn't get in on the first try and a nvlink-minded developer would weigh in :)

I am looking at it and I am still not so sure what exactly guarantees that lifetime(@dev) == lifetime(@pe). For example,
sriov_disable() removes VFs first, and only then releases PEs so there is a window when we may have a stale pdev. Not sure.

  Fred

quoted

quoted

              npu_pdn = pci_get_pdn(npu_pdev);
              rid = npu_pdev->bus->number << 8 | npu_pdn->devfn;
              npu_pdn->pe_number = pe_num;

-- 
Alexey