[dpdk-dev] [PATCH v2] bus/pci: support iova=va on PowerNV systems

[David Christensen <drc@linux.vnet.ibm.com>]

All recent POWER systems, Power 8 and 9 specifically, support an IOMMU
(it can't be disabled). The functionality of the IOMMU is different
depending on whether it's running on a bare metal PowerNV system or in
a virtual environment (PowerVM LPAR or KVM/QEMU).  DPDK currently
supports the IOMMU found on PowerNV platforms, sPAPRv2, so IOVA=VA
mode can be enabled when the correct platform is detected.

The POWER IOMMU type can't be detected through mechansims such as
parsing files in the /sys heirarchy like x86_64 systems so the
/proc/cpuinfo file is parsed to determine whether Linux is running
on bare metal (i.e. PowerNV) or in a virtual environment (KVM/QEMU).

Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
---
v2:
* Fixed memory leak from use of getline
* Fixed nits for NULL memory address and indent levels
* Modified commit message description on logic for detecting IOMMU
  on a POWER system
---
 drivers/bus/pci/linux/pci.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
index 740a2cdad..a1e30b721 100644
--- a/drivers/bus/pci/linux/pci.c
+++ b/drivers/bus/pci/linux/pci.c
@@ -549,7 +549,40 @@ pci_device_iommu_support_va(const struct rte_pci_device *dev)
 bool
 pci_device_iommu_support_va(__rte_unused const struct rte_pci_device *dev)
 {
-	return false;
+	/*
+	 * IOMMU is always present on a PowerNV host (IOMMUv2).
+	 * IOMMU is also present in a KVM/QEMU VM (IOMMUv1) but is not
+	 * currently supported by DPDK. Test for our current environment
+	 * and report VA support as appropriate.
+	 */
+
+	char *line = NULL;
+	size_t len = 0;
+	char filename[PATH_MAX] = "/proc/cpuinfo";
+	FILE *fp = fopen(filename, "r");
+	bool ret = false;
+
+	if (fp == NULL) {
+		RTE_LOG(ERR, EAL, "%s(): can't open %s: %s\n",
+			__func__, filename, strerror(errno));
+		return ret;
+	}
+
+	/* Check for a PowerNV platform */
+	while (getline(&line, &len, fp) != -1) {
+		if (strstr(line, "platform") != NULL)
+			continue;
+
+		if (strstr(line, "PowerNV") != NULL) {
+			RTE_LOG(DEBUG, EAL, "Running on a PowerNV system\n");
+			ret = true;
+			break;
+		}
+	}
+
+	free(line);
+	fclose(fp);
+	return ret;
 }
 #else
 bool
-- 
2.18.1