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SubjectRe: [PATCH v4 2/2] PCI/IOV: Use VF0 cached config space size for other VFs
On Mon, Mar 19, 2018 at 09:06:01PM +0100, KarimAllah Ahmed wrote:
> Cache the config space size from VF0 and use it for all other VFs instead
> of reading it from the config space of each VF. We assume that it will be
> the same across all associated VFs.
>
> This is an optimization when enabling SR-IOV on a device with many VFs.
>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: linux-pci@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>

I didn't apply this one because:

- I don't like the "add two leading underscores to the name"
disease. I'd really like pci_cfg_space_size() to be able to
figure out whether this is VF0 and do the right thing. But I
don't know if we can tell from the pci_dev whether it is VF0. We
do know that every VF is a PCIe device; maybe that's useful
somehow.

- Whatever the name ends up being, it should be declared in
drivers/pci/pci.h, not include/linux/pci.h, because it shouldn't
be used outside the PCI core.

> ---
> drivers/pci/iov.c | 3 +++
> drivers/pci/pci.h | 1 +
> drivers/pci/probe.c | 11 ++++++++++-
> include/linux/pci.h | 1 +
> 4 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 30bf8f7..046e0d3 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -135,6 +135,9 @@ static void pci_read_vf_config_common(struct pci_dev *virtfn)
> &physfn->sriov->subsystem_vendor);
> pci_read_config_word(virtfn, PCI_SUBSYSTEM_ID,
> &physfn->sriov->subsystem_device);
> +
> + virtfn->class = physfn->sriov->class;

Oops, where did this come from? It looks like this belongs in a
different patch because this patch doesn't do anything else with
virtfn->class.

> + physfn->sriov->cfg_size = __pci_cfg_space_size(virtfn);
> }
>
> int pci_iov_add_virtfn(struct pci_dev *dev, int id)
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index bdb4ba2..69da57b 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -271,6 +271,7 @@ 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 cfg_size; /* VF config space size */
> u32 class; /* VF device */
> u8 hdr_type; /* VF header type */
> u16 subsystem_vendor; /* VF subsystem vendor */
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 21ee1c3..fd21e2b 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1365,7 +1365,7 @@ static int pci_cfg_space_size_ext(struct pci_dev *dev)
> return PCI_CFG_SPACE_EXP_SIZE;
> }
>
> -int pci_cfg_space_size(struct pci_dev *dev)
> +int __pci_cfg_space_size(struct pci_dev *dev)
> {
> int pos;
> u32 status;
> @@ -1389,6 +1389,15 @@ int pci_cfg_space_size(struct pci_dev *dev)
> return PCI_CFG_SPACE_SIZE;
> }
>
> +int pci_cfg_space_size(struct pci_dev *dev)
> +{
> +#ifdef CONFIG_PCI_ATS
> + if (dev->is_virtfn)
> + return dev->physfn->sriov->cfg_size;
> +#endif
> + return __pci_cfg_space_size(dev);
> +}
> +
> static int pci_cfg_space_class(struct pci_dev *dev)
> {
> int class;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 024a1be..fcd5d88 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1290,6 +1290,7 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max,
>
> void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
> void *userdata);
> +int __pci_cfg_space_size(struct pci_dev *dev);
> int pci_cfg_space_size(struct pci_dev *dev);
> unsigned char pci_bus_max_busnr(struct pci_bus *bus);
> void pci_setup_bridge(struct pci_bus *bus);
> --
> 2.7.4
>

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