On 2/27/23 8:21 PM, Ganapatrao Kulkarni wrote:
> As per PCI specification (PCI Express Base Specification Revision
> 6.0, Section 10.5) both PF and VFs of a PCI EP are permitted to be enabled
> independently for ATS capability, however the STU(Smallest Translation
> Unit) is shared between PF and VFs. For VFs, it is hardwired to Zero and
> the associated PF's value applies to VFs.
>
> In the current code, the STU is being configured while enabling the PF ATS.
> Hence, it is not able to enable ATS for VFs, if it is not enabled on the
> associated PF already.
>
> Adding a function pci_ats_stu_configure(), which can be called to
> configure the STU during PF enumeration.
> Latter enumerations of VFs can successfully enable ATS independently.
>
> Signed-off-by: Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/pci/ats.c | 33 +++++++++++++++++++++++++++++++--
> include/linux/pci-ats.h | 3 +++
> 2 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index f9cc2e10b676..1611bfa1d5da 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -46,6 +46,35 @@ bool pci_ats_supported(struct pci_dev *dev)
> }
> EXPORT_SYMBOL_GPL(pci_ats_supported);
>
> +/**
> + * pci_ats_stu_configure - Configure STU of a PF.
> + * @dev: the PCI device
> + * @ps: the IOMMU page shift
> + *
> + * Returns 0 on success, or negative on failure.
> + */
> +int pci_ats_stu_configure(struct pci_dev *dev, int ps)
> +{
> + u16 ctrl;
> +
> + if (dev->ats_enabled || dev->is_virtfn)
> + return 0;
Is PF allowed to re-configure STU if there are other active
VF's which uses it?
> +
> + if (!pci_ats_supported(dev))
> + return -EINVAL;
> +
> + if (ps < PCI_ATS_MIN_STU)
> + return -EINVAL;
> +
> + dev->ats_stu = ps;
> + pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, &ctrl);
> + ctrl |= PCI_ATS_CTRL_STU(dev->ats_stu - PCI_ATS_MIN_STU);
> + pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_ats_stu_configure);
> +
> /**
> * pci_enable_ats - enable the ATS capability
> * @dev: the PCI device
> @@ -68,8 +97,8 @@ int pci_enable_ats(struct pci_dev *dev, int ps)
> return -EINVAL;
>
> /*
> - * Note that enabling ATS on a VF fails unless it's already enabled
> - * with the same STU on the PF.
> + * Note that enabling ATS on a VF fails unless it's already
> + * configured with the same STU on the PF.
> */
> ctrl = PCI_ATS_CTRL_ENABLE;
> if (dev->is_virtfn) {
> diff --git a/include/linux/pci-ats.h b/include/linux/pci-ats.h
> index df54cd5b15db..7d62a92aaf23 100644
> --- a/include/linux/pci-ats.h
> +++ b/include/linux/pci-ats.h
> @@ -8,6 +8,7 @@
> /* Address Translation Service */
> bool pci_ats_supported(struct pci_dev *dev);
> int pci_enable_ats(struct pci_dev *dev, int ps);
> +int pci_ats_stu_configure(struct pci_dev *dev, int ps);
> void pci_disable_ats(struct pci_dev *dev);
> int pci_ats_queue_depth(struct pci_dev *dev);
> int pci_ats_page_aligned(struct pci_dev *dev);
> @@ -16,6 +17,8 @@ static inline bool pci_ats_supported(struct pci_dev *d)
> { return false; }
> static inline int pci_enable_ats(struct pci_dev *d, int ps)
> { return -ENODEV; }
> +static inline int pci_ats_stu_configure(struct pci_dev *d, int ps)
> +{ return -ENODEV; }
> static inline void pci_disable_ats(struct pci_dev *d) { }
> static inline int pci_ats_queue_depth(struct pci_dev *d)
> { return -ENODEV; }
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
