Re: [PATCH v5 4/7] PCI/ATS: Add PRI support for PCIe VF devices
From: sathyanarayanan kuppuswamy
Date: Mon Aug 12 2019 - 17:43:17 EST
Hi,
On 8/12/19 1:04 PM, Bjorn Helgaas wrote:
On Thu, Aug 01, 2019 at 05:06:01PM -0700, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
When IOMMU tries to enable Page Request Interface (PRI) for VF device
in iommu_enable_dev_iotlb(), it always fails because PRI support for
PCIe VF device is currently broken. Current implementation expects
the given PCIe device (PF & VF) to implement PRI capability before
enabling the PRI support. But this assumption is incorrect. As per PCIe
spec r4.0, sec 9.3.7.11, all VFs associated with PF can only use the
PRI of the PF and not implement it. Hence we need to create exception
for handling the PRI support for PCIe VF device.
Also, since PRI is a shared resource between PF/VF, following rules
should apply.
1. Use proper locking before accessing/modifying PF resources in VF
PRI enable/disable call.
2. Use reference count logic to track the usage of PRI resource.
3. Disable PRI only if the PRI reference count (pri_ref_cnt) is zero.
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Suggested-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---
drivers/pci/ats.c | 143 ++++++++++++++++++++++++++++++++++----------
include/linux/pci.h | 2 +
2 files changed, 112 insertions(+), 33 deletions(-)
diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 1f4be27a071d..079dc5444444 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -189,6 +189,8 @@ void pci_pri_init(struct pci_dev *pdev)
if (pdev->is_virtfn)
return;
+ mutex_init(&pdev->pri_lock);
+
pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
if (!pos)
return;
@@ -221,29 +223,57 @@ int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
{
u16 control, status;
u32 max_requests;
+ int ret = 0;
+ struct pci_dev *pf = pci_physfn(pdev);
- if (WARN_ON(pdev->pri_enabled))
- return -EBUSY;
+ mutex_lock(&pf->pri_lock);
- if (!pdev->pri_cap)
- return -EINVAL;
+ if (WARN_ON(pdev->pri_enabled)) {
+ ret = -EBUSY;
+ goto pri_unlock;
+ }
- pci_read_config_word(pdev, pdev->pri_cap + PCI_PRI_STATUS, &status);
- if (!(status & PCI_PRI_STATUS_STOPPED))
- return -EBUSY;
+ if (!pf->pri_cap) {
+ ret = -EINVAL;
+ goto pri_unlock;
+ }
+
+ if (pdev->is_virtfn && pf->pri_enabled)
+ goto update_status;
+
+ /*
+ * Before updating PRI registers, make sure there is no
+ * outstanding PRI requests.
+ */
+ pci_read_config_word(pf, pf->pri_cap + PCI_PRI_STATUS, &status);
+ if (!(status & PCI_PRI_STATUS_STOPPED)) {
+ ret = -EBUSY;
+ goto pri_unlock;
+ }
- pci_read_config_dword(pdev, pdev->pri_cap + PCI_PRI_MAX_REQ,
- &max_requests);
+ pci_read_config_dword(pf, pf->pri_cap + PCI_PRI_MAX_REQ, &max_requests);
reqs = min(max_requests, reqs);
- pdev->pri_reqs_alloc = reqs;
- pci_write_config_dword(pdev, pdev->pri_cap + PCI_PRI_ALLOC_REQ, reqs);
+ pf->pri_reqs_alloc = reqs;
+ pci_write_config_dword(pf, pf->pri_cap + PCI_PRI_ALLOC_REQ, reqs);
control = PCI_PRI_CTRL_ENABLE;
- pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
+ pci_write_config_word(pf, pf->pri_cap + PCI_PRI_CTRL, control);
- pdev->pri_enabled = 1;
+ /*
+ * If PRI is not already enabled in PF, increment the PF
+ * pri_ref_cnt to track the usage of PRI interface.
+ */
+ if (pdev->is_virtfn && !pf->pri_enabled) {
+ atomic_inc(&pf->pri_ref_cnt);
+ pf->pri_enabled = 1;
+ }
- return 0;
+update_status:
+ atomic_inc(&pf->pri_ref_cnt);
+ pdev->pri_enabled = 1;
+pri_unlock:
+ mutex_unlock(&pf->pri_lock);
+ return ret;
}
EXPORT_SYMBOL_GPL(pci_enable_pri);
@@ -256,18 +286,30 @@ EXPORT_SYMBOL_GPL(pci_enable_pri);
void pci_disable_pri(struct pci_dev *pdev)
{
u16 control;
+ struct pci_dev *pf = pci_physfn(pdev);
- if (WARN_ON(!pdev->pri_enabled))
- return;
+ mutex_lock(&pf->pri_lock);
- if (!pdev->pri_cap)
- return;
+ if (WARN_ON(!pdev->pri_enabled) || !pf->pri_cap)
+ goto pri_unlock;
+
+ atomic_dec(&pf->pri_ref_cnt);
- pci_read_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, &control);
+ /*
+ * If pri_ref_cnt is not zero, then don't modify hardware
+ * registers.
+ */
+ if (atomic_read(&pf->pri_ref_cnt))
+ goto done;
+
+ pci_read_config_word(pf, pf->pri_cap + PCI_PRI_CTRL, &control);
control &= ~PCI_PRI_CTRL_ENABLE;
- pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
+ pci_write_config_word(pf, pf->pri_cap + PCI_PRI_CTRL, control);
+done:
pdev->pri_enabled = 0;
+pri_unlock:
+ mutex_unlock(&pf->pri_lock);
}
EXPORT_SYMBOL_GPL(pci_disable_pri);
@@ -277,17 +319,31 @@ EXPORT_SYMBOL_GPL(pci_disable_pri);
*/
void pci_restore_pri_state(struct pci_dev *pdev)
{
- u16 control = PCI_PRI_CTRL_ENABLE;
- u32 reqs = pdev->pri_reqs_alloc;
+ u16 control;
+ u32 reqs;
+ struct pci_dev *pf = pci_physfn(pdev);
if (!pdev->pri_enabled)
return;
- if (!pdev->pri_cap)
+ if (!pf->pri_cap)
return;
- pci_write_config_dword(pdev, pdev->pri_cap + PCI_PRI_ALLOC_REQ, reqs);
- pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
+ mutex_lock(&pf->pri_lock);
+
+ /* If PRI is already enabled by other VF's or PF, return */
+ pci_read_config_word(pf, pf->pri_cap + PCI_PRI_CTRL, &control);
+ if (control & PCI_PRI_CTRL_ENABLE)
+ goto pri_unlock;
+
+ reqs = pf->pri_reqs_alloc;
+ control = PCI_PRI_CTRL_ENABLE;
+
+ pci_write_config_dword(pf, pf->pri_cap + PCI_PRI_ALLOC_REQ, reqs);
+ pci_write_config_word(pf, pf->pri_cap + PCI_PRI_CTRL, control);
Why use "control" here instead of just PCI_PRI_CTRL_ENABLE?
It can be done. Even in original code, using control did not serve any
purpose. I just left the implementation as original code.
+pri_unlock:
+ mutex_unlock(&pf->pri_lock);
}
EXPORT_SYMBOL_GPL(pci_restore_pri_state);
@@ -300,18 +356,32 @@ EXPORT_SYMBOL_GPL(pci_restore_pri_state);
*/
int pci_reset_pri(struct pci_dev *pdev)
{
+ struct pci_dev *pf = pci_physfn(pdev);
u16 control;
+ int ret = 0;
- if (WARN_ON(pdev->pri_enabled))
- return -EBUSY;
+ mutex_lock(&pf->pri_lock);
- if (!pdev->pri_cap)
- return -EINVAL;
+ if (WARN_ON(pdev->pri_enabled)) {
+ ret = -EBUSY;
+ goto done;
+ }
+
+ if (!pf->pri_cap) {
+ ret = -EINVAL;
+ goto done;
+ }
+
+ /* If PRI is already enabled by other VF's or PF, return 0 */
+ if (pf->pri_enabled)
+ goto done;
control = PCI_PRI_CTRL_RESET;
- pci_write_config_word(pdev, pdev->pri_cap + PCI_PRI_CTRL, control);
- return 0;
+ pci_write_config_word(pf, pf->pri_cap + PCI_PRI_CTRL, control);
Also here (you didn't add this one, but "control" is completely
pointless in this function).
+done:
+ mutex_unlock(&pf->pri_lock);
+ return ret;
}
EXPORT_SYMBOL_GPL(pci_reset_pri);
#endif /* CONFIG_PCI_PRI */
@@ -475,11 +545,18 @@ EXPORT_SYMBOL_GPL(pci_pasid_features);
int pci_prg_resp_pasid_required(struct pci_dev *pdev)
{
u16 status;
+ struct pci_dev *pf = pci_physfn(pdev);
+
+ mutex_lock(&pf->pri_lock);
- if (!pdev->pri_cap)
+ if (!pf->pri_cap) {
+ mutex_unlock(&pf->pri_lock);
return 0;
+ }
+
+ pci_read_config_word(pf, pf->pri_cap + PCI_PRI_STATUS, &status);
- pci_read_config_word(pdev, pdev->pri_cap + PCI_PRI_STATUS, &status);
+ mutex_unlock(&pf->pri_lock);
if (status & PCI_PRI_STATUS_PASID)
return 1;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 27224c0db849..3c9c4c82be27 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -455,8 +455,10 @@ struct pci_dev {
atomic_t ats_ref_cnt; /* Number of VFs with ATS enabled */
#endif
#ifdef CONFIG_PCI_PRI
+ struct mutex pri_lock; /* PRI enable lock */
u16 pri_cap; /* PRI Capability offset */
u32 pri_reqs_alloc; /* Number of PRI requests allocated */
+ atomic_t pri_ref_cnt; /* Number of PF/VF PRI users */
#endif
#ifdef CONFIG_PCI_PASID
u16 pasid_cap; /* PASID Capability offset */
--
2.21.0
--
Sathyanarayanan Kuppuswamy
Linux kernel developer