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SubjectRe: [PATCH v2 2/5] PCI/ATS: Add PASID support for PCIe VF devices
On Mon, May 06, 2019 at 10:20:04AM -0700, sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>
> When IOMMU tries to enable PASID for VF device in
> iommu_enable_dev_iotlb(), it always fails because PASID support for PCIe
> VF device is currently broken in PCIE driver. Current implementation
> expects the given PCIe device (PF & VF) to implement PASID capability
> before enabling the PASID support. But this assumption is incorrect. As
> per PCIe spec r4.0, sec 9.3.7.14, all VFs associated with PF can only
> use the PASID of the PF and not implement it.
>
> Since PASID is shared between PF/VF devices, following rules should
> apply.
>
> 1. Enable PASID in VF only if its already enabled in PF.

s/its/it's/ (same comment applies to PRI patch, IIRC)

> 2. Enable PASID in VF only if the requested features matches with PF
> config, otherwise return error.
> 3. When enabling/disabling PASID for VF, instead of configuring the PF
> registers just increase/decrease the usage count (pasid_ref_cnt).
> 4. Disable PASID in PF (configuring the registers) only if pasid_ref_cnt
> is zero.
> 5. When reading PASID features/settings for VF, use registers of
> corresponding PF.
>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Keith Busch <keith.busch@intel.com>
> Suggested-by: Ashok Raj <ashok.raj@intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> ---
> drivers/pci/ats.c | 55 ++++++++++++++++++++++++++++++++++++++++++++-
> include/linux/pci.h | 1 +
> 2 files changed, 55 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index 5582e5d83a3f..e7a904e347c3 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -345,6 +345,7 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
> {
> u16 control, supported;
> int pos;
> + struct pci_dev *pf;
>
> if (WARN_ON(pdev->pasid_enabled))
> return -EBUSY;
> @@ -353,7 +354,33 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
> return -EINVAL;
>
> pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
> - if (!pos)
> +
> + if (pdev->is_virtfn) {
> + /*
> + * Per PCIe r4.0, sec 9.3.7.14, VF must not implement
> + * Process Address Space ID (PASID) Capability.
> + */
> + if (pos) {
> + dev_err(&pdev->dev, "VF must not implement PASID\n");
> + return -EINVAL
> + }

Same comment as for PRI.

> + /* Since VF shares PASID with PF, use PF config */
> + pf = pci_physfn(pdev);
> +
> + /* If VF config does not match with PF, return error */
> + if (!pf->pasid_enabled || pf->pasid_features != features)
> + return -EINVAL;
> +
> + pdev->pasid_features = features;

I don't think this is used for VFs.

> + pdev->pasid_enabled = 1;
> +
> + /* Increment PF PASID refcount */
> + atomic_inc(&pf->pasid_ref_cnt);
> +
> + return 0;
> + }
> +
> + if (pdev->is_physfn && !pos)
> return -EINVAL;
>
> pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);
> @@ -382,10 +409,27 @@ void pci_disable_pasid(struct pci_dev *pdev)
> {
> u16 control = 0;
> int pos;
> + struct pci_dev *pf;
>
> if (WARN_ON(!pdev->pasid_enabled))
> return;
>
> + /* All VFs PASID should be disabled before disabling PF PASID*/

Add space at end of comment.

> + if (atomic_read(&pdev->pasid_ref_cnt))
> + return;
> +
> + if (pdev->is_virtfn) {
> + /* Since VF shares PASID with PF, use PF config. */

Most single-line, single-sentence comments here do not include a
trailing period.

> + pf = pci_physfn(pdev);
> +
> + /* Decrement PF PASID refcount */
> + atomic_dec(&pf->pasid_ref_cnt);
> +
> + pdev->pasid_enabled = 0;
> +
> + return;
> + }
> +
> pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
> if (!pos)
> return;
> @@ -408,6 +452,9 @@ void pci_restore_pasid_state(struct pci_dev *pdev)
> if (!pdev->pasid_enabled)
> return;
>
> + if (pdev->is_virtfn)
> + return;
> +
> pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
> if (!pos)
> return;
> @@ -432,6 +479,9 @@ int pci_pasid_features(struct pci_dev *pdev)
> u16 supported;
> int pos;
>
> + if (pdev->is_virtfn)
> + pdev = pci_physfn(pdev);
> +
> pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
> if (!pos)
> return -EINVAL;
> @@ -488,6 +538,9 @@ int pci_max_pasids(struct pci_dev *pdev)
> u16 supported;
> int pos;
>
> + if (pdev->is_virtfn)
> + pdev = pci_physfn(pdev);
> +
> pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
> if (!pos)
> return -EINVAL;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 699c79c99a39..2a761ea63f8d 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -454,6 +454,7 @@ struct pci_dev {
> #endif
> #ifdef CONFIG_PCI_PASID
> u16 pasid_features;
> + atomic_t pasid_ref_cnt; /* Number of VFs with PASID enabled */
> #endif
> #ifdef CONFIG_PCI_P2PDMA
> struct pci_p2pdma *p2pdma;
> --
> 2.20.1
>

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