[dpdk-dev] [PATCH v2 2/3] eal: compute IOVA mode based on PA availability

[David Marchand]

From: Ben Walker <benjamin.walker at intel.com>

Currently, if the bus selects IOVA as PA, the memory init can fail when
lacking access to physical addresses.
This can be quite hard for normal users to understand what is wrong
since this is the default behavior.

Catch this situation earlier in eal init by validating physical addresses
availability, or select IOVA when no clear preferrence had been expressed.

The bus code is changed so that it reports when it does not care about
the IOVA mode and let the eal init decide.

In Linux implementation, rework rte_eal_using_phys_addrs() so that it can
be called earlier but still avoid a circular dependency with
rte_mem_virt2phys().
In FreeBSD implementation, rte_eal_using_phys_addrs() always returns
false, so the detection part is left as is.

If librte_kni is compiled in and the KNI kmod is loaded,
- if the buses requested VA, force to PA if physical addresses are
  available as it was done before,
- else, keep iova as VA, KNI init will fail later.

Signed-off-by: Ben Walker <benjamin.walker at intel.com>
Signed-off-by: David Marchand <david.marchand at redhat.com>
---
 lib/librte_eal/common/eal_common_bus.c  |  4 ---
 lib/librte_eal/common/include/rte_bus.h |  2 +-
 lib/librte_eal/freebsd/eal/eal.c        | 10 +++++--
 lib/librte_eal/linux/eal/eal.c          | 38 +++++++++++++++++++++------
 lib/librte_eal/linux/eal/eal_memory.c   | 46 +++++++++------------------------
 5 files changed, 51 insertions(+), 49 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_bus.c b/lib/librte_eal/common/eal_common_bus.c
index c8f1901..77f1be1 100644
--- a/lib/librte_eal/common/eal_common_bus.c
+++ b/lib/librte_eal/common/eal_common_bus.c
@@ -237,10 +237,6 @@ enum rte_iova_mode
 			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/common/include/rte_bus.h b/lib/librte_eal/common/include/rte_bus.h
index 4faf2d2..90fe4e9 100644
--- a/lib/librte_eal/common/include/rte_bus.h
+++ b/lib/librte_eal/common/include/rte_bus.h
@@ -392,7 +392,7 @@ struct rte_bus *rte_bus_find(const struct rte_bus *start, rte_bus_cmp_t cmp,
 
 /**
  * Get the common iommu class of devices bound on to buses available in the
- * system. The default mode is PA.
+ * system. RTE_IOVA_DC means that no preferrence has been expressed.
  *
  * @return
  *     enum rte_iova_mode value.
diff --git a/lib/librte_eal/freebsd/eal/eal.c b/lib/librte_eal/freebsd/eal/eal.c
index 4eaa531..231f1dc 100644
--- a/lib/librte_eal/freebsd/eal/eal.c
+++ b/lib/librte_eal/freebsd/eal/eal.c
@@ -689,13 +689,19 @@ static void rte_eal_init_alert(const char *msg)
 	/* 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();
+		enum rte_iova_mode iova_mode = rte_bus_get_iommu_class();
+
+		if (iova_mode == RTE_IOVA_DC)
+			iova_mode = RTE_IOVA_PA;
+		rte_eal_get_configuration()->iova_mode = iova_mode;
 	} else {
 		rte_eal_get_configuration()->iova_mode =
 			internal_config.iova_mode;
 	}
 
+	RTE_LOG(INFO, EAL, "Selected IOVA mode '%s'\n",
+		rte_eal_iova_mode() == RTE_IOVA_PA ? "PA" : "VA");
+
 	if (internal_config.no_hugetlbfs == 0) {
 		/* rte_config isn't initialized yet */
 		ret = internal_config.process_type == RTE_PROC_PRIMARY ?
diff --git a/lib/librte_eal/linux/eal/eal.c b/lib/librte_eal/linux/eal/eal.c
index 3e1d6eb..785ed2b 100644
--- a/lib/librte_eal/linux/eal/eal.c
+++ b/lib/librte_eal/linux/eal/eal.c
@@ -948,6 +948,7 @@ static void rte_eal_init_alert(const char *msg)
 	static char logid[PATH_MAX];
 	char cpuset[RTE_CPU_AFFINITY_STR_LEN];
 	char thread_name[RTE_MAX_THREAD_NAME_LEN];
+	bool phys_addrs;
 
 	/* checks if the machine is adequate */
 	if (!rte_cpu_is_supported()) {
@@ -1035,25 +1036,46 @@ static void rte_eal_init_alert(const char *msg)
 		return -1;
 	}
 
+	phys_addrs = rte_eal_using_phys_addrs() != 0;
+
 	/* 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 */
+		enum rte_iova_mode iova_mode = rte_bus_get_iommu_class();
 
+		if (iova_mode == RTE_IOVA_DC) {
+			iova_mode = phys_addrs ? RTE_IOVA_PA : RTE_IOVA_VA;
+			RTE_LOG(DEBUG, EAL,
+				"Buses did not request a specific IOVA mode, using '%s' based on physical addresses availability.\n",
+				phys_addrs ? "PA" : "VA");
+		}
+#ifdef RTE_LIBRTE_KNI
 		/* 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;
-			RTE_LOG(WARNING, EAL,
-				"Some devices want IOVA as VA but PA will be used because.. "
-				"KNI module inserted\n");
+			if (phys_addrs) {
+				iova_mode = RTE_IOVA_PA;
+				RTE_LOG(WARNING, EAL, "Forcing IOVA as 'PA' because KNI module is loaded\n");
+			} else {
+				RTE_LOG(DEBUG, EAL, "KNI can not work since physical addresses are unavailable\n");
+			}
 		}
+#endif
+		rte_eal_get_configuration()->iova_mode = iova_mode;
 	} else {
 		rte_eal_get_configuration()->iova_mode =
 			internal_config.iova_mode;
 	}
 
+	if (rte_eal_iova_mode() == RTE_IOVA_PA && !phys_addrs) {
+		rte_eal_init_alert("Cannot use IOVA as 'PA' since physical addresses are not available");
+		rte_errno = EINVAL;
+		return -1;
+	}
+
+	RTE_LOG(INFO, EAL, "Selected IOVA mode '%s'\n",
+		rte_eal_iova_mode() == RTE_IOVA_PA ? "PA" : "VA");
+
 	if (internal_config.no_hugetlbfs == 0) {
 		/* rte_config isn't initialized yet */
 		ret = internal_config.process_type == RTE_PROC_PRIMARY ?
diff --git a/lib/librte_eal/linux/eal/eal_memory.c b/lib/librte_eal/linux/eal/eal_memory.c
index 1853ace..25c4145 100644
--- a/lib/librte_eal/linux/eal/eal_memory.c
+++ b/lib/librte_eal/linux/eal/eal_memory.c
@@ -65,34 +65,10 @@
  * zone as well as a physical contiguous zone.
  */
 
-static bool phys_addrs_available = true;
+static int phys_addrs_available = -1;
 
 #define RANDOMIZE_VA_SPACE_FILE "/proc/sys/kernel/randomize_va_space"
 
-static void
-test_phys_addrs_available(void)
-{
-	uint64_t tmp = 0;
-	phys_addr_t physaddr;
-
-	if (!rte_eal_has_hugepages()) {
-		RTE_LOG(ERR, EAL,
-			"Started without hugepages support, physical addresses not available\n");
-		phys_addrs_available = false;
-		return;
-	}
-
-	physaddr = rte_mem_virt2phy(&tmp);
-	if (physaddr == RTE_BAD_PHYS_ADDR) {
-		if (rte_eal_iova_mode() == RTE_IOVA_PA)
-			RTE_LOG(ERR, EAL,
-				"Cannot obtain physical addresses: %s. "
-				"Only vfio will function.\n",
-				strerror(errno));
-		phys_addrs_available = false;
-	}
-}
-
 /*
  * Get physical address of any mapped virtual address in the current process.
  */
@@ -105,8 +81,7 @@
 	int page_size;
 	off_t offset;
 
-	/* Cannot parse /proc/self/pagemap, no need to log errors everywhere */
-	if (!phys_addrs_available)
+	if (phys_addrs_available == 0)
 		return RTE_BAD_IOVA;
 
 	/* standard page size */
@@ -1336,8 +1311,6 @@ void numa_error(char *where)
 	int nr_hugefiles, nr_hugepages = 0;
 	void *addr;
 
-	test_phys_addrs_available();
-
 	memset(used_hp, 0, sizeof(used_hp));
 
 	/* get pointer to global configuration */
@@ -1516,7 +1489,7 @@ void numa_error(char *where)
 				continue;
 		}
 
-		if (phys_addrs_available &&
+		if (rte_eal_using_phys_addrs() &&
 				rte_eal_iova_mode() != RTE_IOVA_VA) {
 			/* find physical addresses for each hugepage */
 			if (find_physaddrs(&tmp_hp[hp_offset], hpi) < 0) {
@@ -1735,8 +1708,6 @@ void numa_error(char *where)
 	uint64_t memory[RTE_MAX_NUMA_NODES];
 	int hp_sz_idx, socket_id;
 
-	test_phys_addrs_available();
-
 	memset(used_hp, 0, sizeof(used_hp));
 
 	for (hp_sz_idx = 0;
@@ -1879,8 +1850,6 @@ void numa_error(char *where)
 				"into secondary processes\n");
 	}
 
-	test_phys_addrs_available();
-
 	fd_hugepage = open(eal_hugepage_data_path(), O_RDONLY);
 	if (fd_hugepage < 0) {
 		RTE_LOG(ERR, EAL, "Could not open %s\n",
@@ -2020,6 +1989,15 @@ void numa_error(char *where)
 int
 rte_eal_using_phys_addrs(void)
 {
+	if (phys_addrs_available == -1) {
+		uint64_t tmp = 0;
+
+		if (rte_eal_has_hugepages() != 0 &&
+		    rte_mem_virt2phy(&tmp) != RTE_BAD_PHYS_ADDR)
+			phys_addrs_available = 1;
+		else
+			phys_addrs_available = 0;
+	}
 	return phys_addrs_available;
 }
 
-- 
1.8.3.1