10-Bit Tag capability, introduced in PCIe-4.0 increases the total Tag
field size from 8 bits to 10 bits.
PCIe spec 5.0 r1.0 section 2.2.6.2 "Considerations for Implementing
10-Bit Tag Capabilities" Implementation Note:
For platforms where the RC supports 10-Bit Tag Completer capability,
it is highly recommended for platform firmware or operating software
that configures PCIe hierarchies to Set the 10-Bit Tag Requester Enable
bit automatically in Endpoints with 10-Bit Tag Requester capability.
This enables the important class of 10-Bit Tag capable adapters that
send Memory Read Requests only to host memory.
It's safe to enable 10-bit tags for all devices below a Root Port that
supports them. Switches that lack 10-Bit Tag Completer capability are
still able to forward NPRs and Completions carrying 10-Bit Tags correctly,
since the two new Tag bits are in TLP Header bits that were formerly
Reserved.
PCIe spec 5.0 r1.0 section 2.2.6.2 says:
If an Endpoint supports sending Requests to other Endpoints (as opposed
to host memory), the Endpoint must not send 10-Bit Tag Requests to
another given Endpoint unless an implementation-specific mechanism
determines that the Endpoint supports 10-Bit Tag Completer capability.
It is not safe for P2P traffic if an Endpoint send 10-Bit Tag Requesters
to another Endpoint that does not support 10-Bit Tag Completer capability,
so we provide sysfs file to disable 10-Bit Tag Requester. Unbind the
device driver, set the sysfs file and then rebind the driver.
Add a kernel parameter pcie_tag_peer2peer that disables 10-Bit Tag
Requester for all PCIe devices. This configuration allows peer-to-peer
DMA between any pair of devices, possibly at the cost of reduced
performance.
Signed-off-by: Dongdong Liu <liudongdong3@xxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 5 +++
drivers/pci/iov.c | 3 ++
drivers/pci/pci-sysfs.c | 3 ++
drivers/pci/pci.c | 4 ++
drivers/pci/pci.h | 7 ++++
drivers/pci/probe.c | 42 ++++++++++++++++++-
6 files changed, 63 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 43dc35fe5bc0..4ab2c46a1af7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3979,6 +3979,11 @@
any pair of devices, possibly at the cost of
reduced performance. This also guarantees
that hot-added devices will work.
+ pcie_tag_peer2peer Disable 10-Bit Tag Requester for all
+ PCIe devices. This configuration allows
+ peer-to-peer DMA between any pair of devices,
+ possibly at the cost of reduced performance.
+
cbiosize=nn[KMG] The fixed amount of bus space which is
reserved for the CardBus bridge's IO window.
The default value is 256 bytes.
diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 3627e495d7af..0f8203ccc701 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -241,6 +241,9 @@ static ssize_t sriov_vf_tags_ctl_store(struct device *dev,
if (vf_dev->driver)
return -EBUSY;
+ if (pcie_tag_config == PCIE_TAG_PEER2PEER)
+ return -EPERM;
+
if (!pcie_rp_10bit_tag_cmp_supported(pdev))
return -EPERM;
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 04fd9a8b9d4e..71647bb3ac06 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -326,6 +326,9 @@ static ssize_t tags_store(struct device *dev,
if (pdev->driver)
return -EBUSY;
+ if (pcie_tag_config == PCIE_TAG_PEER2PEER)
+ return -EPERM;
+
if (!pcie_rp_10bit_tag_cmp_supported(pdev))
return -EPERM;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 64138a83b0f7..46faf2e8c8ab 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -118,6 +118,8 @@ enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_PEER2PEER;
enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_DEFAULT;
#endif
+enum pcie_tag_config_types pcie_tag_config = PCIE_TAG_DEFAULT;
+
/*
* The default CLS is used if arch didn't set CLS explicitly and not
* all pci devices agree on the same value. Arch can override either
@@ -6795,6 +6797,8 @@ static int __init pci_setup(char *str)
pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
} else if (!strncmp(str, "disable_acs_redir=", 18)) {
disable_acs_redir_param = str + 18;
+ } else if (!strncmp(str, "pcie_tag_peer2peer", 18)) {
+ pcie_tag_config = PCIE_TAG_PEER2PEER;
} else {
pr_err("PCI: Unknown option `%s'\n", str);
}
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index f719a41dfc7f..7846aa7b85dc 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -59,6 +59,13 @@ struct pci_cap_saved_state *pci_find_saved_cap(struct pci_dev *dev, char cap);
struct pci_cap_saved_state *pci_find_saved_ext_cap(struct pci_dev *dev,
u16 cap);
+enum pcie_tag_config_types {
+ PCIE_TAG_DEFAULT, /* Enable 10-Bit Tag Requester for devices below
+ Root Port that support 10-Bit Tag Completer. */
+ PCIE_TAG_PEER2PEER /* Disable 10-Bit Tag Requester for all devices. */
+};
+extern enum pcie_tag_config_types pcie_tag_config;
+
#define PCI_PM_D2_DELAY 200 /* usec; see PCIe r4.0, sec 5.9.1 */
#define PCI_PM_D3HOT_WAIT 10 /* msec */
#define PCI_PM_D3COLD_WAIT 100 /* msec */
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8f5372c7c737..18a74e257dd9 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2059,12 +2059,20 @@ bool pcie_rp_10bit_tag_cmp_supported(struct pci_dev *dev)
int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
{
struct pci_host_bridge *host;
- u16 ctl;
+ u16 ctl, ctl2;
int ret;
if (!pci_is_pcie(dev))
return 0;
+ /*
+ * PCIe 5.0 section 9.3.5.4 Extended Tag Field Enable in Device Control
+ * Register is RsvdP fo VF. section 9.3.5.10 10-Bit Tag Requester
+ * Enable in Device Control 2 Register is RsvdP for VF.
+ */
+ if (dev->is_virtfn)
+ return 0;
+
if (!(dev->devcap & PCI_EXP_DEVCAP_EXT_TAG))
return 0;
@@ -2072,6 +2080,10 @@ int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
if (ret)
return 0;
+ ret = pcie_capability_read_word(dev, PCI_EXP_DEVCTL2, &ctl2);
+ if (ret)
+ return 0;
+
host = pci_find_host_bridge(dev->bus);
if (!host)
return 0;
@@ -2086,6 +2098,12 @@ int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
PCI_EXP_DEVCTL_EXT_TAG);
}
+
+ if (ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN) {
+ pci_info(dev, "disabling 10-Bit Tags\n");
+ pcie_capability_clear_word(dev, PCI_EXP_DEVCTL2,
+ PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
+ }
return 0;
}
@@ -2100,6 +2118,28 @@ int pci_configure_extended_tags(struct pci_dev *dev, void *ign)
pcie_capability_set_word(dev, PCI_EXP_DEVCTL,
PCI_EXP_DEVCTL_EXT_TAG);
}
+
+ if ((pcie_tag_config == PCIE_TAG_PEER2PEER) &&
+ (ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN)) {
+ pci_info(dev, "disabling 10-Bit Tags\n");
+ pcie_capability_clear_word(dev, PCI_EXP_DEVCTL2,
+ PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
+ return 0;
+ }
+
+ if (pcie_tag_config != PCIE_TAG_DEFAULT)
+ return 0;
+
+ if (!pcie_rp_10bit_tag_cmp_supported(dev))
+ return 0;
+
+ if (pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT)
+ return 0;
+
+ pci_dbg(dev, "enabling 10-Bit Tag Requester\n");
+ pcie_capability_set_word(dev, PCI_EXP_DEVCTL2,
+ PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
+
return 0;
}
--
2.22.0
