[dpdk-dev] [PATCH 12/12] eal: If bus can't decide PA or VA, try to access PA

[Ben Walker]

If the bus can't determine a preference for IOVA_PA vs.
IOVA_VA by looking at the devices and drivers, as a
last resort test if physical addresses are even accessible
in /proc/self/pagemap. If they are, use IOVA_PA. If they
are not, use IOVA_VA.

Change-Id: If1eeb723283b80b24bd973987054fdad62f59cbd
---
 lib/librte_eal/common/eal_common_bus.c |  4 ----
 lib/librte_eal/linux/eal/eal.c         | 28 +++++++++++++++++++-------
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_bus.c 
b/lib/librte_eal/common/eal_common_bus.c
index c8f1901f0..77f1be1b4 100644
--- a/lib/librte_eal/common/eal_common_bus.c
+++ b/lib/librte_eal/common/eal_common_bus.c
@@ -237,10 +237,6 @@ rte_bus_get_iommu_class(void)
                        mode |= bus->get_iommu_class();
        }
 
-       if (mode != RTE_IOVA_VA) {
-               /* Use default IOVA mode */
-               mode = RTE_IOVA_PA;
-       }
        return mode;
 }
 
diff --git a/lib/librte_eal/linux/eal/eal.c b/lib/librte_eal/linux/eal/eal.c
index 161399619..283aae120 100644
--- a/lib/librte_eal/linux/eal/eal.c
+++ b/lib/librte_eal/linux/eal/eal.c
@@ -948,6 +948,7 @@ rte_eal_init(int argc, char **argv)
        static char logid[PATH_MAX];
        char cpuset[RTE_CPU_AFFINITY_STR_LEN];
        char thread_name[RTE_MAX_THREAD_NAME_LEN];
+       enum rte_iova_mode iova_mode;
 
        /* checks if the machine is adequate */
        if (!rte_cpu_is_supported()) {
@@ -1037,18 +1038,31 @@ rte_eal_init(int argc, char **argv)
 
        /* if no EAL option "--iova-mode=<pa|va>", use bus IOVA scheme */
        if (internal_config.iova_mode == RTE_IOVA_DC) {
-               /* autodetect the IOVA mapping mode (default is RTE_IOVA_PA) */
-               rte_eal_get_configuration()->iova_mode =
-                       rte_bus_get_iommu_class();
+               /* autodetect the IOVA mapping mode */
+               iova_mode = rte_bus_get_iommu_class();
 
                /* Workaround for KNI which requires physical address to work */
-               if (rte_eal_get_configuration()->iova_mode == RTE_IOVA_VA &&
+               if (iova_mode == RTE_IOVA_VA &&
                                rte_eal_check_module("rte_kni") == 1) {
-                       rte_eal_get_configuration()->iova_mode = RTE_IOVA_PA;
+                       iova_mode = RTE_IOVA_PA;
                        RTE_LOG(WARNING, EAL,
-                               "Some devices want IOVA as VA but PA will be 
used because.. "
-                               "KNI module inserted\n");
+                               "Some devices want IOVA as VA but PA will be"
+                               " used because KNI module inserted\n");
+               }
+
+               if (iova_mode == RTE_IOVA_DC) {
+                       /* If the bus doesn't care, check if physical addresses 
are
+                        * accessible. */
+                       if (rte_eal_using_phys_addrs()) {
+                               /* Physical addresses are available, so the 
safest
+                                * choice is to use those. */
+                               iova_mode = RTE_IOVA_PA;
+                       } else {
+                               iova_mode = RTE_IOVA_VA;
+                       }
                }
+
+               rte_eal_get_configuration()->iova_mode = iova_mode;
        } else {
                rte_eal_get_configuration()->iova_mode =
                        internal_config.iova_mode;
-- 
2.20.1