Re: [PATCH v3 1/2] PCI/IOV: Store more data about VFs into the SRIOV struct
From: Bjorn Helgaas
Date: Fri Mar 02 2018 - 16:36:46 EST
On Thu, Mar 01, 2018 at 10:31:36PM +0100, KarimAllah Ahmed wrote:
> Store more data about PCI VFs into the SRIOV to avoid reading them from the
> config space of all the PCI VFs. This is specially a useful optimization
> when bringing up thousands of VFs.
>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: linux-pci@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
Applied to pci/virtualization for v4.17, thanks!
I removed the pci_sriov.device field, which seemed to be unused, and
tweaked a few other things, so make sure I didn't break anything. Here's
what I have currently applied:
commit e17b7b429b095200f93ad37c4efeb7a99b6fce3b
Author: KarimAllah Ahmed <karahmed@xxxxxxxxx>
Date: Thu Mar 1 22:31:36 2018 +0100
PCI/IOV: Use VF0 cached config registers for other VFs
Cache some config data from VF0 and use it for all other VFs instead of
reading it from the config space of each VF. We assume these items are the
same across all associated VFs:
Revision ID
Class Code
Subsystem Vendor ID
Subsystem ID
This is an optimization when enabling SR-IOV on a device with many VFs.
Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
[bhelgaas: changelog, simplify comments, remove unused "device"]
Signed-off-by: Bjorn Helgaas <helgaas@xxxxxxxxxx>
diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 677924ae0350..30bf8f706ed9 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -114,6 +114,29 @@ resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
return dev->sriov->barsz[resno - PCI_IOV_RESOURCES];
}
+static void pci_read_vf_config_common(struct pci_dev *virtfn)
+{
+ struct pci_dev *physfn = virtfn->physfn;
+
+ /*
+ * Some config registers are the same across all associated VFs.
+ * Read them once from VF0 so we can skip reading them from the
+ * other VFs.
+ *
+ * PCIe r4.0, sec 9.3.4.1, technically doesn't require all VFs to
+ * have the same Revision ID and Subsystem ID, but we assume they
+ * do.
+ */
+ pci_read_config_dword(virtfn, PCI_CLASS_REVISION,
+ &physfn->sriov->class);
+ pci_read_config_byte(virtfn, PCI_HEADER_TYPE,
+ &physfn->sriov->hdr_type);
+ pci_read_config_word(virtfn, PCI_SUBSYSTEM_VENDOR_ID,
+ &physfn->sriov->subsystem_vendor);
+ pci_read_config_word(virtfn, PCI_SUBSYSTEM_ID,
+ &physfn->sriov->subsystem_device);
+}
+
int pci_iov_add_virtfn(struct pci_dev *dev, int id)
{
int i;
@@ -136,13 +159,17 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
virtfn->devfn = pci_iov_virtfn_devfn(dev, id);
virtfn->vendor = dev->vendor;
virtfn->device = iov->vf_device;
+ virtfn->is_virtfn = 1;
+ virtfn->physfn = pci_dev_get(dev);
+
+ if (id == 0)
+ pci_read_vf_config_common(virtfn);
+
rc = pci_setup_device(virtfn);
if (rc)
- goto failed0;
+ goto failed1;
virtfn->dev.parent = dev->dev.parent;
- virtfn->physfn = pci_dev_get(dev);
- virtfn->is_virtfn = 1;
virtfn->multifunction = 0;
for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
@@ -163,10 +190,10 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
sprintf(buf, "virtfn%u", id);
rc = sysfs_create_link(&dev->dev.kobj, &virtfn->dev.kobj, buf);
if (rc)
- goto failed1;
+ goto failed2;
rc = sysfs_create_link(&virtfn->dev.kobj, &dev->dev.kobj, "physfn");
if (rc)
- goto failed2;
+ goto failed3;
kobject_uevent(&virtfn->dev.kobj, KOBJ_CHANGE);
@@ -174,11 +201,12 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
return 0;
-failed2:
+failed3:
sysfs_remove_link(&dev->dev.kobj, buf);
+failed2:
+ pci_stop_and_remove_bus_device(virtfn);
failed1:
pci_dev_put(dev);
- pci_stop_and_remove_bus_device(virtfn);
failed0:
virtfn_remove_bus(dev->bus, bus);
failed:
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index fcd81911b127..db76933be859 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -271,6 +271,10 @@ struct pci_sriov {
u16 driver_max_VFs; /* Max num VFs driver supports */
struct pci_dev *dev; /* Lowest numbered PF */
struct pci_dev *self; /* This PF */
+ u32 class; /* VF class */
+ u8 hdr_type; /* VF header type */
+ u16 subsystem_vendor; /* VF subsystem vendor */
+ u16 subsystem_device; /* VF subsystem device */
resource_size_t barsz[PCI_SRIOV_NUM_BARS]; /* VF BAR size */
bool drivers_autoprobe; /* Auto probing of VFs by driver */
};
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index a1cddca37793..78deb950bda1 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1461,7 +1461,9 @@ int pci_setup_device(struct pci_dev *dev)
struct pci_bus_region region;
struct resource *res;
- if (pci_read_config_byte(dev, PCI_HEADER_TYPE, &hdr_type))
+ if (dev->is_virtfn)
+ hdr_type = dev->physfn->sriov->hdr_type;
+ else if (pci_read_config_byte(dev, PCI_HEADER_TYPE, &hdr_type))
return -EIO;
dev->sysdata = dev->bus->sysdata;
@@ -1484,7 +1486,10 @@ int pci_setup_device(struct pci_dev *dev)
dev->bus->number, PCI_SLOT(dev->devfn),
PCI_FUNC(dev->devfn));
- pci_read_config_dword(dev, PCI_CLASS_REVISION, &class);
+ if (dev->is_virtfn)
+ class = dev->physfn->sriov->class;
+ else
+ pci_read_config_dword(dev, PCI_CLASS_REVISION, &class);
dev->revision = class & 0xff;
dev->class = class >> 8; /* upper 3 bytes */
@@ -1524,8 +1529,13 @@ int pci_setup_device(struct pci_dev *dev)
goto bad;
pci_read_irq(dev);
pci_read_bases(dev, 6, PCI_ROM_ADDRESS);
- pci_read_config_word(dev, PCI_SUBSYSTEM_VENDOR_ID, &dev->subsystem_vendor);
- pci_read_config_word(dev, PCI_SUBSYSTEM_ID, &dev->subsystem_device);
+ if (dev->is_virtfn) {
+ dev->subsystem_vendor = dev->physfn->sriov->subsystem_vendor;
+ dev->subsystem_device = dev->physfn->sriov->subsystem_device;
+ } else {
+ pci_read_config_word(dev, PCI_SUBSYSTEM_VENDOR_ID, &dev->subsystem_vendor);
+ pci_read_config_word(dev, PCI_SUBSYSTEM_ID, &dev->subsystem_device);
+ }
/*
* Do the ugly legacy mode stuff here rather than broken chip