[PATCH v3 2/2] PCI/IOV: Use the cached VF BARs size instead of re-reading them

From: KarimAllah Ahmed
Date: Thu Mar 01 2018 - 16:32:04 EST


Use the cached VF BARs size instead of re-reading them from the hardware.
That avoids doing unnecessarily bus transactions which is specially
noticable when you have a PF with a large number of VFs.

Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
---
drivers/pci/probe.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index a96837e..aeaa10a 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -180,6 +180,7 @@ static inline unsigned long decode_bar(struct pci_dev *dev, u32 bar)
int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
struct resource *res, unsigned int pos)
{
+ int bar = res - dev->resource;
u32 l = 0, sz = 0, mask;
u64 l64, sz64, mask64;
u16 orig_cmd;
@@ -199,9 +200,13 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
res->name = pci_name(dev);

pci_read_config_dword(dev, pos, &l);
- pci_write_config_dword(dev, pos, l | mask);
- pci_read_config_dword(dev, pos, &sz);
- pci_write_config_dword(dev, pos, l);
+ if (dev->is_virtfn) {
+ sz = dev->physfn->sriov->barsz[bar] & 0xffffffff;
+ } else {
+ pci_write_config_dword(dev, pos, l | mask);
+ pci_read_config_dword(dev, pos, &sz);
+ pci_write_config_dword(dev, pos, l);
+ }

/*
* All bits set in sz means the device isn't working properly.
@@ -241,9 +246,14 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,

if (res->flags & IORESOURCE_MEM_64) {
pci_read_config_dword(dev, pos + 4, &l);
- pci_write_config_dword(dev, pos + 4, ~0);
- pci_read_config_dword(dev, pos + 4, &sz);
- pci_write_config_dword(dev, pos + 4, l);
+
+ if (dev->is_virtfn) {
+ sz = (dev->physfn->sriov->barsz[bar] >> 32) & 0xffffffff;
+ } else {
+ pci_write_config_dword(dev, pos + 4, ~0);
+ pci_read_config_dword(dev, pos + 4, &sz);
+ pci_write_config_dword(dev, pos + 4, l);
+ }

l64 |= ((u64)l << 32);
sz64 |= ((u64)sz << 32);
@@ -332,6 +342,8 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
for (pos = 0; pos < howmany; pos++) {
struct resource *res = &dev->resource[pos];
reg = PCI_BASE_ADDRESS_0 + (pos << 2);
+ if (dev->is_virtfn && dev->physfn->sriov->barsz[pos] == 0)
+ continue;
pos += __pci_read_base(dev, pci_bar_unknown, res, reg);
}

--
2.7.4