Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

From: sathyanarayanan kuppuswamy
Date: Wed Jun 12 2019 - 14:48:20 EST



On 6/12/19 11:19 AM, Alex Williamson wrote:
On Wed, 12 Jun 2019 10:06:47 -0700
sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
other VFs") calculates and caches the cfg_size for VF0 device before
initializing the pcie_cap of the device which results in using incorrect
cfg_size for all VF devices > 0. So set pcie_cap of the device before
calculating the cfg_size of VF0 device.

Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
other VFs")
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Suggested-by: Mike Campin <mike.campin@xxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---

Changes since v1:
* Fixed a typo in commit message.

drivers/pci/iov.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 3aa115ed3a65..2869011c0e35 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
virtfn->device = iov->vf_device;
virtfn->is_virtfn = 1;
virtfn->physfn = pci_dev_get(dev);
+ virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
if (id == 0)
pci_read_vf_config_common(virtfn);
Why not re-order until after we've setup pcie_cap?

https://lore.kernel.org/linux-pci/20190604143617.0a226555@xxxxxxx/T/#

pci_read_vf_config_common() also caches values for properties like class, hdr_type, susbsystem_vendor/device. These values are read/used in pci_setup_device(). So if we can use cached values in pci_setup_device(), we don't have to read them from registers twice for each device.


Thanks,
Alex

--
Sathyanarayanan Kuppuswamy
Linux kernel developer