Re: [PATCH v7 1/2] bus/pci: support PASID control

[David Marchand <david.marchand@redhat.com>]

On Mon, Nov 6, 2023 at 6:05 PM Abdullah Sevincer
<abdullah.sevincer@intel.com> wrote:
>
> Add an internal API to control PASID for a given PCIe device.
>
> For kernels when PASID enabled by default it breaks DLB functionality,
> hence disabling PASID is required for DLB to function properly.
>
> PASID capability is not exposed to users hence offset can not be
> retrieved by rte_pci_find_ext_capability() api. Therefore, api
> implemented in this commit accepts an offset for PASID with an enable
> flag which is used to enable/disable PASID.
>
> Signed-off-by: Abdullah Sevincer <abdullah.sevincer@intel.com>
> ---
>  drivers/bus/pci/pci_common.c  |  7 +++++++
>  drivers/bus/pci/rte_bus_pci.h | 13 +++++++++++++
>  drivers/bus/pci/version.map   |  1 +
>  lib/pci/rte_pci.h             |  4 ++++
>  4 files changed, 25 insertions(+)
>
> diff --git a/drivers/bus/pci/pci_common.c b/drivers/bus/pci/pci_common.c
> index 921d957bf6..ecf080c5d7 100644
> --- a/drivers/bus/pci/pci_common.c
> +++ b/drivers/bus/pci/pci_common.c
> @@ -938,6 +938,13 @@ rte_pci_set_bus_master(const struct rte_pci_device *dev, bool enable)
>         return 0;
>  }
>
> +int
> +rte_pci_pasid_set_state(const struct rte_pci_device *dev, off_t offset, bool enable)
> +{
> +       uint16_t pasid = enable;
> +       return rte_pci_write_config(dev, &pasid, sizeof(pasid), offset) < 0 ? -1 : 0;
> +}

I don't see much point in providing a wrapper that does nothing more
than call rte_pci_write_config() and let the driver pass the right
offsets.

If anything, can't this wrapper find out about the pasid offset itself?
There is a extended capability for this, so I would expect it can be used.

Something like (only compile tested):

diff --git a/drivers/bus/pci/pci_common.c b/drivers/bus/pci/pci_common.c
index ba5e280d33..2ca28bd4d4 100644
--- a/drivers/bus/pci/pci_common.c
+++ b/drivers/bus/pci/pci_common.c
@@ -939,13 +939,18 @@ rte_pci_set_bus_master(const struct
rte_pci_device *dev, bool enable)
 }

 int
-rte_pci_pasid_set_state(const struct rte_pci_device *dev,
-               off_t offset, bool enable)
+rte_pci_pasid_set_state(const struct rte_pci_device *dev, bool enable)
 {
-       uint16_t pasid = enable;
-       return rte_pci_write_config(dev, &pasid, sizeof(pasid), offset) < 0
-               ? -1
-               : 0;
+       uint16_t state = enable;
+       off_t pasid_offset;
+       int ret = -1;
+
+       pasid_offset = rte_pci_find_ext_capability(dev,
RTE_PCI_EXT_CAP_ID_PASID);
+       if (pasid_offset >= 0 && rte_pci_write_config(dev, &state,
sizeof(state),
+                       pasid_offset + RTE_PCI_PASID_CTRL) == sizeof(state))
+               ret = 0;
+
+       return ret;
 }

 struct rte_pci_bus rte_pci_bus = {
diff --git a/drivers/bus/pci/rte_bus_pci.h b/drivers/bus/pci/rte_bus_pci.h
index f07bf9b588..6d5dbc1d50 100644
--- a/drivers/bus/pci/rte_bus_pci.h
+++ b/drivers/bus/pci/rte_bus_pci.h
@@ -160,14 +160,14 @@ int rte_pci_set_bus_master(const struct
rte_pci_device *dev, bool enable);
  *
  * @param dev
  *   A pointer to a rte_pci_device structure.
- * @param offset
- *   Offset of the PASID external capability.
  * @param enable
  *   Flag to enable or disable PASID.
+ *
+ *  @return
+ *  0 on success, -1 on error in PCI config space read/write.
  */
 __rte_internal
-int rte_pci_pasid_set_state(const struct rte_pci_device *dev,
-               off_t offset, bool enable);
+int rte_pci_pasid_set_state(const struct rte_pci_device *dev, bool enable);

 /**
  * Read PCI config space.
diff --git a/drivers/event/dlb2/pf/dlb2_main.c
b/drivers/event/dlb2/pf/dlb2_main.c
index 61a7b39eef..bd1ee4af27 100644
--- a/drivers/event/dlb2/pf/dlb2_main.c
+++ b/drivers/event/dlb2/pf/dlb2_main.c
@@ -26,7 +26,6 @@
 #define PF_ID_ZERO 0   /* PF ONLY! */
 #define NO_OWNER_VF 0  /* PF ONLY! */
 #define NOT_VF_REQ false /* PF ONLY! */
-#define DLB2_PCI_PASID_CAP_OFFSET        0x148   /* PASID capability offset */

 static int
 dlb2_pf_init_driver_state(struct dlb2_dev *dlb2_dev)
@@ -518,8 +517,7 @@ dlb2_pf_reset(struct dlb2_dev *dlb2_dev)
        /* Disable PASID if it is enabled by default, which
         * breaks the DLB if enabled.
         */
-       off = DLB2_PCI_PASID_CAP_OFFSET + RTE_PCI_PASID_CTRL;
-       if (rte_pci_pasid_set_state(pdev, off, false)) {
+       if (rte_pci_pasid_set_state(pdev, false)) {
                DLB2_LOG_ERR("[%s()] failed to write the pcie config
space at offset %d\n",
                                __func__, (int)off);
                return -1;


-- 
David Marchand