[RFC PATCH 2/4] PCI: Add "pci=iommu_passthrough=" parameter for iommu passthrough

Lu Baolu
2020-01-01T05:37:05Z

The new parameter takes a list of devices separated by a semicolon.
Each device specified will have its iommu_passthrough bit in struct
device set. This is very similar to the existing 'disable_acs_redir'
parameter.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
.../admin-guide/kernel-parameters.txt | 5 +++
drivers/pci/pci.c | 34 +++++++++++++++++++
drivers/pci/pci.h | 1 +
drivers/pci/probe.c | 2 ++
4 files changed, 42 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ade4e6ec23e0..d3edc2cb6696 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3583,6 +3583,11 @@
may put more devices in an IOMMU group.
force_floating [S390] Force usage of floating interrupts.
nomio [S390] Do not use MIO instructions.
+ iommu_passthrough=<pci_dev>[; ...]
+ Specify one or more PCI devices (in the format
+ specified above) separated by semicolons.
+ Each device specified will bypass IOMMU DMA
+ translation.

pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 90dbd7c70371..05bf3f4acc36 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6401,6 +6401,37 @@ void __weak pci_fixup_cardbus(struct pci_bus *bus)
}
EXPORT_SYMBOL(pci_fixup_cardbus);

+static const char *iommu_passthrough_param;
+bool pci_iommu_passthrough_match(struct pci_dev *dev)
+{
+ int ret = 0;
+ const char *p = iommu_passthrough_param;
+
+ if (!p)
+ return false;
+
+ while (*p) {
+ ret = pci_dev_str_match(dev, p, &p);
+ if (ret < 0) {
+ pr_info_once("PCI: Can't parse iommu_passthrough parameter: %s\n",
+ iommu_passthrough_param);
+
+ break;
+ } else if (ret == 1) {
+ pci_info(dev, "PCI: IOMMU passthrough\n");
+ return true;
+ }
+
+ if (*p != ';' && *p != ',') {
+ /* End of param or invalid format */
+ break;
+ }
+ p++;
+ }
+
+ return false;
+}
+
static int __init pci_setup(char *str)
{
while (str) {
@@ -6462,6 +6493,8 @@ 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, "iommu_passthrough=", 18)) {
+ iommu_passthrough_param = str + 18;
} else {
pr_err("PCI: Unknown option `%s'\n", str);
}
@@ -6486,6 +6519,7 @@ 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);
+ iommu_passthrough_param = kstrdup(iommu_passthrough_param, GFP_KERNEL);

return 0;
}
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index a0a53bd05a0b..95f6af06aba6 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -288,6 +288,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev);
void pci_disable_bridge_window(struct pci_dev *dev);
struct pci_bus *pci_bus_get(struct pci_bus *bus);
void pci_bus_put(struct pci_bus *bus);
+bool pci_iommu_passthrough_match(struct pci_dev *dev);

/* PCIe link information */
#define PCIE_SPEED2STR(speed) \
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 512cb4312ddd..4c571ee75621 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2404,6 +2404,8 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)

dev->state_saved = false;

+ dev->dev.iommu_passthrough = pci_iommu_passthrough_match(dev);
+
pci_init_capabilities(dev);

/*
--
2.17.1