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Subject[PATCH v3 1/1] PCI: Add translated request only flag for pci_enable_pasid()
The PCIe fabric routes Memory Requests based on the TLP address, ignoring
the PASID. In order to ensure system integrity, commit 201007ef707a ("PCI:
Enable PASID only when ACS RR & UF enabled on upstream path") requires
some ACS features being supported on device's upstream path when enabling

One alternative is ATS/PRI which lets the device resolve the PASID + addr
pair before a memory request is made into a routeable TLB address through
the translation agent. Those resolved addresses are then cached on the
device instead of in the IOMMU TLB and the device always sets translated
bit for PASID. One example of those devices are AMD graphic devices that
always have ACS or ATS/PRI enabled together with PASID.

This adds a flag parameter in the pci_enable_pasid() helper, with which
the device driver could opt-in the fact that device always sets the
translated bit for PASID.

It also applies this opt-in for AMD graphic devices. Without this change,
kernel boots to black screen on a system with below AMD graphic device:

00:01.0 VGA compatible controller: Advanced Micro Devices, Inc.
[AMD/ATI] Wani [Radeon R5/R6/R7 Graphics] (rev ca)
(prog-if 00 [VGA controller])
Subsystem: Hewlett-Packard Company Device 8332

At present, it is a common practice to enable/disable PCI PASID in the
iommu drivers. Considering that the device driver knows more about the
specific device, we will follow up by moving pci_enable_pasid() into
the specific device drivers.

Fixes: 201007ef707a ("PCI: Enable PASID only when ACS RR & UF enabled on upstream path")
Reported-and-tested-by: Matt Fagnani <>
Suggested-by: Jason Gunthorpe <>
Suggested-by: Christian König <>
Reviewed-by: Kevin Tian <>
Signed-off-by: Lu Baolu <>
include/linux/pci-ats.h | 6 ++++--
drivers/iommu/amd/iommu.c | 2 +-
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
drivers/iommu/intel/iommu.c | 3 ++-
drivers/pci/ats.c | 8 ++++++--
5 files changed, 14 insertions(+), 7 deletions(-)

Change log:
- Replace ATS with ATS/PRI in commit message;
- Refine a code comment;
- Patch tested by Matt Fagnani.
- Convert the bool to a named flag;

diff --git a/include/linux/pci-ats.h b/include/linux/pci-ats.h
index df54cd5b15db..750fca736ef4 100644
--- a/include/linux/pci-ats.h
+++ b/include/linux/pci-ats.h
@@ -4,6 +4,8 @@

#include <linux/pci.h>

/* Address Translation Service */
bool pci_ats_supported(struct pci_dev *dev);
@@ -35,12 +37,12 @@ static inline bool pci_pri_supported(struct pci_dev *pdev)
#endif /* CONFIG_PCI_PRI */

-int pci_enable_pasid(struct pci_dev *pdev, int features);
+int pci_enable_pasid(struct pci_dev *pdev, int features, int flags);
void pci_disable_pasid(struct pci_dev *pdev);
int pci_pasid_features(struct pci_dev *pdev);
int pci_max_pasids(struct pci_dev *pdev);
#else /* CONFIG_PCI_PASID */
-static inline int pci_enable_pasid(struct pci_dev *pdev, int features)
+static inline int pci_enable_pasid(struct pci_dev *pdev, int features, int flags)
{ return -EINVAL; }
static inline void pci_disable_pasid(struct pci_dev *pdev) { }
static inline int pci_pasid_features(struct pci_dev *pdev)
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index cbeaab55c0db..64a8c03d7dfa 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -1700,7 +1700,7 @@ static int pdev_pri_ats_enable(struct pci_dev *pdev)
int ret;

/* Only allow access to user-accessible pages */
- ret = pci_enable_pasid(pdev, 0);
+ ret = pci_enable_pasid(pdev, 0, PCI_PASID_XLATED_REQ_ONLY);
if (ret)
goto out_err;

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index ab160198edd6..891bf53c45dc 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2350,7 +2350,7 @@ static int arm_smmu_enable_pasid(struct arm_smmu_master *master)
if (num_pasids <= 0)
return num_pasids;

- ret = pci_enable_pasid(pdev, features);
+ ret = pci_enable_pasid(pdev, features, 0);
if (ret) {
dev_err(&pdev->dev, "Failed to enable PASID\n");
return ret;
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 59df7e42fd53..5cc13f02a5ac 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1425,7 +1425,8 @@ static void iommu_enable_pci_caps(struct device_domain_info *info)
undefined. So always enable PASID support on devices which
have it, even if we can't yet know if we're ever going to
use it. */
- if (info->pasid_supported && !pci_enable_pasid(pdev, info->pasid_supported & ~1))
+ if (info->pasid_supported &&
+ !pci_enable_pasid(pdev, info->pasid_supported & ~1, 0))
info->pasid_enabled = 1;

if (info->pri_supported &&
diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index f9cc2e10b676..06168415d6d7 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -353,12 +353,15 @@ void pci_pasid_init(struct pci_dev *pdev)
* pci_enable_pasid - Enable the PASID capability
* @pdev: PCI device structure
* @features: Features to enable
+ * @flags: device-specific flags
+ * - PCI_PASID_XLATED_REQ_ONLY: The PCI device always use translated type
+ * for all PASID memory requests.
* Returns 0 on success, negative value on error. This function checks
* whether the features are actually supported by the device and returns
* an error if not.
-int pci_enable_pasid(struct pci_dev *pdev, int features)
+int pci_enable_pasid(struct pci_dev *pdev, int features, int flags)
u16 control, supported;
int pasid = pdev->pasid_cap;
@@ -382,7 +385,8 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
if (!pasid)
return -EINVAL;

- if (!pci_acs_path_enabled(pdev, NULL, PCI_ACS_RR | PCI_ACS_UF))
+ if (!(flags & PCI_PASID_XLATED_REQ_ONLY) &&
+ !pci_acs_path_enabled(pdev, NULL, PCI_ACS_RR | PCI_ACS_UF))
return -EINVAL;

pci_read_config_word(pdev, pasid + PCI_PASID_CAP, &supported);
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