Re: [PATCH] pci: Do not read INTx PIN and LINE registers for virtual functions

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 01/17/2018 07:49 PM, Alex Williamson wrote:
On Wed, 17 Jan 2018 19:30:29 +0100
KarimAllah Ahmed <karahmed@xxxxxxxxx> wrote:

... since INTx is not supported by-spec for virtual functions.
But the spec also states that VFs must implement the interrupt pin
register as read-only zero, so either this is redundant or it's a
workaround for VFs that aren't quite compliant?  Thanks,

The end goal for me is just to NOT do the read across the PCI bus for no good reason. We have devices with thousands of virtual functions and this read is simply not useful in this case and can be optimized as I did. So from a functionality point of view probably the patch does not add any value as you mentioned, but it is really useful as a micro-optimization.


Alex

Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
Signed-off-by: Jan H. Schönherr <jschoenh@xxxxxxxxx>
---
  drivers/pci/probe.c | 7 +++++++
  1 file changed, 7 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 65099d0..61002fb 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1232,6 +1232,13 @@ static void pci_read_irq(struct pci_dev *dev)
  {
  	unsigned char irq;
+ /* Virtual functions do not have INTx support */
+	if (dev->is_virtfn) {
+		dev->pin = 0;
+		dev->irq = 0;
+		return;
+	}
+
  	pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &irq);
  	dev->pin = irq;
  	if (irq)


Amazon Development Center Germany GmbH
Berlin - Dresden - Aachen
main office: Krausenstr. 38, 10117 Berlin
Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger
Ust-ID: DE289237879
Eingetragen am Amtsgericht Charlottenburg HRB 149173 B




[Index of Archives]     [DMA Engine]     [Linux Coverity]     [Linux USB]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Greybus]

  Powered by Linux