[PATCH V2] PCI: Extend ACS configurability
From: Vidya Sagar
Date: Tue May 21 2024 - 07:10:11 EST
For iommu_groups to form correctly, the ACS settings in the PCIe fabric
need to be setup early in the boot process, either via the BIOS or via
the kernel disable_acs_redir parameter.
disable_acs_redir allows clearing the RR|CR|EC ACS flags, but the PCIe
spec Rev3.0 already defines 7 different ACS related flags with many more
useful combinations depending on the fabric design.
For backward compatibility, leave the 'disable_acs_redir' as is and add
a new parameter 'config_acs'so that the user can directly specify the ACS
flags to set on a per-device basis. Use a similar syntax to the existing
'resource_alignment' parameter by using the @ character and have the user
specify the ACS flags using a bit encoding. If both 'disable_acs_redir' and
'config_acs' are specified for a particular device, configuration specified
through 'config_acs' takes precedence over the other.
Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
---
v2:
* Refactored the code as per Jason's suggestion
.../admin-guide/kernel-parameters.txt | 22 +++
drivers/pci/pci.c | 147 +++++++++++-------
2 files changed, 111 insertions(+), 58 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 41644336e..b4a8207eb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4456,6 +4456,28 @@
bridges without forcing it upstream. Note:
this removes isolation between devices and
may put more devices in an IOMMU group.
+ config_acs=
+ Format:
+ =<ACS flags>@<pci_dev>[; ...]
+ Specify one or more PCI devices (in the format
+ specified above) optionally prepended with flags
+ and separated by semicolons. The respective
+ capabilities will be enabled, disabled or unchanged
+ based on what is specified in flags.
+ ACS Flags is defined as follows
+ bit-0 : ACS Source Validation
+ bit-1 : ACS Translation Blocking
+ bit-2 : ACS P2P Request Redirect
+ bit-3 : ACS P2P Completion Redirect
+ bit-4 : ACS Upstream Forwarding
+ bit-5 : ACS P2P Egress Control
+ bit-6 : ACS Direct Translated P2P
+ Each bit can be marked as
+ ‘0‘ – force disabled
+ ‘1’ – force enabled
+ ‘x’ – unchanged.
+ Note: this may remove isolation between devices
+ and may put more devices in an IOMMU group.
force_floating [S390] Force usage of floating interrupts.
nomio [S390] Do not use MIO instructions.
norid [S390] ignore the RID field and force use of
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index a607f277c..862df97f1 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -887,30 +887,67 @@ void pci_request_acs(void)
}
static const char *disable_acs_redir_param;
+static const char *config_acs_param;
-/**
- * pci_disable_acs_redir - disable ACS redirect capabilities
- * @dev: the PCI device
- *
- * For only devices specified in the disable_acs_redir parameter.
- */
-static void pci_disable_acs_redir(struct pci_dev *dev)
+struct pci_acs {
+ u16 cap;
+ u16 ctrl;
+ u16 fw_ctrl;
+};
+
+static void __pci_config_acs(struct pci_dev *dev, struct pci_acs *caps,
+ const char *p, u16 mask, u16 flags)
{
+ char *delimit;
int ret = 0;
- const char *p;
- int pos;
- u16 ctrl;
- if (!disable_acs_redir_param)
+ if (!p)
return;
- p = disable_acs_redir_param;
while (*p) {
+ if (!mask) {
+ /* Check for ACS flags */
+ delimit = strstr(p, "@");
+ if (delimit) {
+ int end;
+ u32 shift = 0;
+
+ end = delimit - p - 1;
+
+ while (end > -1) {
+ if (*(p + end) == '0') {
+ mask |= 1 << shift;
+ shift++;
+ end--;
+ } else if (*(p + end) == '1') {
+ mask |= 1 << shift;
+ flags |= 1 << shift;
+ shift++;
+ end--;
+ } else if ((*(p + end) == 'x') || (*(p + end) == 'X')) {
+ shift++;
+ end--;
+ } else {
+ pci_err(dev, "Invalid ACS flags... Ignoring\n");
+ return;
+ }
+ }
+ p = delimit + 1;
+ } else {
+ pci_err(dev, "ACS Flags missing\n");
+ return;
+ }
+ }
+
+ if (mask & ~(PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR | PCI_ACS_CR |
+ PCI_ACS_UF | PCI_ACS_EC | PCI_ACS_DT)) {
+ pci_err(dev, "Invalid ACS flags specified\n");
+ return;
+ }
+
ret = pci_dev_str_match(dev, p, &p);
if (ret < 0) {
- pr_info_once("PCI: Can't parse disable_acs_redir parameter: %s\n",
- disable_acs_redir_param);
-
+ pr_info_once("PCI: Can't parse acs command line parameter\n");
break;
} else if (ret == 1) {
/* Found a match */
@@ -930,56 +967,37 @@ static void pci_disable_acs_redir(struct pci_dev *dev)
if (!pci_dev_specific_disable_acs_redir(dev))
return;
- pos = dev->acs_cap;
- if (!pos) {
- pci_warn(dev, "cannot disable ACS redirect for this hardware as it does not have ACS capabilities\n");
- return;
- }
-
- pci_read_config_word(dev, pos + PCI_ACS_CTRL, &ctrl);
+ pci_dbg(dev, "ACS mask = 0x%X\n", mask);
+ pci_dbg(dev, "ACS flags = 0x%X\n", flags);
- /* P2P Request & Completion Redirect */
- ctrl &= ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC);
+ /* If mask is 0 then we copy the bit from the firmware setting. */
+ caps->ctrl = (caps->ctrl & ~mask) | (caps->fw_ctrl & mask);
+ caps->ctrl |= flags;
- pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
-
- pci_info(dev, "disabled ACS redirect\n");
+ pci_info(dev, "Configured ACS to 0x%x\n", caps->ctrl);
}
/**
* pci_std_enable_acs - enable ACS on devices using standard ACS capabilities
* @dev: the PCI device
*/
-static void pci_std_enable_acs(struct pci_dev *dev)
+static void pci_std_enable_acs(struct pci_dev *dev, struct pci_acs *caps)
{
- int pos;
- u16 cap;
- u16 ctrl;
-
- pos = dev->acs_cap;
- if (!pos)
- return;
-
- pci_read_config_word(dev, pos + PCI_ACS_CAP, &cap);
- pci_read_config_word(dev, pos + PCI_ACS_CTRL, &ctrl);
-
/* Source Validation */
- ctrl |= (cap & PCI_ACS_SV);
+ caps->ctrl |= (caps->cap & PCI_ACS_SV);
/* P2P Request Redirect */
- ctrl |= (cap & PCI_ACS_RR);
+ caps->ctrl |= (caps->cap & PCI_ACS_RR);
/* P2P Completion Redirect */
- ctrl |= (cap & PCI_ACS_CR);
+ caps->ctrl |= (caps->cap & PCI_ACS_CR);
/* Upstream Forwarding */
- ctrl |= (cap & PCI_ACS_UF);
+ caps->ctrl |= (caps->cap & PCI_ACS_UF);
/* Enable Translation Blocking for external devices and noats */
if (pci_ats_disabled() || dev->external_facing || dev->untrusted)
- ctrl |= (cap & PCI_ACS_TB);
-
- pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
+ caps->ctrl |= (caps->cap & PCI_ACS_TB);
}
/**
@@ -988,23 +1006,33 @@ static void pci_std_enable_acs(struct pci_dev *dev)
*/
static void pci_enable_acs(struct pci_dev *dev)
{
- if (!pci_acs_enable)
- goto disable_acs_redir;
+ struct pci_acs caps;
+ int pos;
+
+ pos = dev->acs_cap;
+ if (!pos)
+ return;
- if (!pci_dev_specific_enable_acs(dev))
- goto disable_acs_redir;
+ pci_read_config_word(dev, pos + PCI_ACS_CAP, &caps.cap);
+ pci_read_config_word(dev, pos + PCI_ACS_CTRL, &caps.ctrl);
+ caps.fw_ctrl = caps.ctrl;
- pci_std_enable_acs(dev);
+ /* If an iommu is present we start with kernel default caps */
+ if (pci_acs_enable) {
+ if (pci_dev_specific_enable_acs(dev))
+ pci_std_enable_acs(dev, &caps);
+ }
-disable_acs_redir:
/*
- * Note: pci_disable_acs_redir() must be called even if ACS was not
- * enabled by the kernel because it may have been enabled by
- * platform firmware. So if we are told to disable it, we should
- * always disable it after setting the kernel's default
- * preferences.
+ * Always apply caps from the command line, even if there is no iommu.
+ * Trust that the admin has a reason to change the ACS settings.
*/
- pci_disable_acs_redir(dev);
+ __pci_config_acs(dev, &caps, disable_acs_redir_param,
+ PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC,
+ ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC));
+ __pci_config_acs(dev, &caps, config_acs_param, 0, 0);
+
+ pci_write_config_word(dev, pos + PCI_ACS_CTRL, caps.ctrl);
}
/**
@@ -7023,6 +7051,8 @@ 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, "config_acs=", 11)) {
+ config_acs_param = str + 11;
} else {
pr_err("PCI: Unknown option `%s'\n", str);
}
@@ -7047,6 +7077,7 @@ static int __init pci_realloc_setup_params(void)
resource_alignment_param = kstrdup(resource_alignment_param,
GFP_KERNEL);
disable_acs_redir_param = kstrdup(disable_acs_redir_param, GFP_KERNEL);
+ config_acs_param = kstrdup(config_acs_param, GFP_KERNEL);
return 0;
}
--
2.25.1