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Date: Tue, 6 Mar 2018 10:37:02 +0000
From: "Raslan, KarimAllah" <karahmed@...zon.de>
To: "helgaas@...nel.org" <helgaas@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"bhelgaas@...gle.com" <bhelgaas@...gle.com>
Subject: Re: [PATCH v3 1/2] PCI/IOV: Store more data about VFs into the SRIOV
struct
On Fri, 2018-03-02 at 15:36 -0600, Bjorn Helgaas wrote:
> 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@...gle.com>
> > Cc: linux-pci@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Signed-off-by: KarimAllah Ahmed <karahmed@...zon.de>
>
> 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.
Yup, still looks good (and works) for me. Thanks.
> Here's what I have currently applied:
>
> commit e17b7b429b095200f93ad37c4efeb7a99b6fce3b
> Author: KarimAllah Ahmed <karahmed@...zon.de>
> 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@...zon.de>
> [bhelgaas: changelog, simplify comments, remove unused "device"]
> Signed-off-by: Bjorn Helgaas <helgaas@...nel.org>
>
> 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
>
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