[Qemu-devel] [kvm-unit-tests PATCH v5 09/11] arm: query /dev/kvm for maximum vcpus

["Alex Bennée" <alex.bennee@linaro.org>]

From: Alex Bennée <alex@bennee.com>

The previous $(getconf _NPROCESSORS_CONF) isn't correct as the default
maximum VCPU configuration is 4 on arm64 machines which typically have
more actual cores.

This introduces a simple utility program to query the KVM capabilities
and use the correct maximum number of vcpus.

[FOR DISCUSSION: this fails on TCG which could use _NPROCESSORS_CONF]

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 arm/unittests.cfg            | 10 +++++-----
 arm/utils/kvm-query.c        | 41 +++++++++++++++++++++++++++++++++++++++++
 config/config-arm-common.mak |  8 +++++++-
 3 files changed, 53 insertions(+), 6 deletions(-)
 create mode 100644 arm/utils/kvm-query.c

diff --git a/arm/unittests.cfg b/arm/unittests.cfg
index 19d72ad..7a3a32b 100644
--- a/arm/unittests.cfg
+++ b/arm/unittests.cfg
@@ -32,30 +32,30 @@ groups = selftest
 # Test SMP support
 [selftest::smp]
 file = selftest.flat
-smp = $(getconf _NPROCESSORS_CONF)
+smp = $(./arm/utils/kvm-query max_vcpu)
 extra_params = -append 'smp'
 groups = selftest
 
 # TLB Torture Tests
 [tlbflush::all_other]
 file = tlbflush-test.flat
-smp = $(getconf _NPROCESSORS_CONF)
+smp = $(./arm/utils/kvm-query max_vcpu)
 groups = tlbflush
 
 [tlbflush::page_other]
 file = tlbflush-test.flat
-smp = $(getconf _NPROCESSORS_CONF)
+smp = $(./arm/utils/kvm-query max_vcpu)
 extra_params = -append 'page'
 groups = tlbflush
 
 [tlbflush::all_self]
 file = tlbflush-test.flat
-smp = $(getconf _NPROCESSORS_CONF)
+smp = $(./arm/utils/kvm-query max_vcpu)
 extra_params = -append 'self'
 groups = tlbflush
 
 [tlbflush::page_self]
 file = tlbflush-test.flat
-smp = $(getconf _NPROCESSORS_CONF)
+smp = $(./arm/utils/kvm-query max_vcpu)
 extra_params = -append 'page self'
 groups = tlbflush
diff --git a/arm/utils/kvm-query.c b/arm/utils/kvm-query.c
new file mode 100644
index 0000000..4f979b1
--- /dev/null
+++ b/arm/utils/kvm-query.c
@@ -0,0 +1,41 @@
+/*
+ * kvm-query.c
+ *
+ * A simple utility to query KVM capabilities.
+ */
+
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <string.h>
+#include <stdio.h>
+
+#include <linux/kvm.h>
+
+int get_max_vcpu(void)
+{
+	int fd = open("/dev/kvm", O_RDWR);
+	if (fd>0) {
+		int ret = ioctl(fd, KVM_CHECK_EXTENSION, KVM_CAP_MAX_VCPUS);
+		printf("%d\n", ret > 0 ? ret : 0);
+		close(fd);
+		return 0;
+	} else {
+		return -1;
+	}
+}
+
+int main(int argc, char **argv)
+{
+	for (int i=0; i<argc; i++) {
+		char *arg = argv[i];
+		if (strcmp(arg, "max_vcpu") == 0) {
+			return get_max_vcpu();
+		}
+	}
+
+	return  -1;
+}
diff --git a/config/config-arm-common.mak b/config/config-arm-common.mak
index 164199b..9c7607b 100644
--- a/config/config-arm-common.mak
+++ b/config/config-arm-common.mak
@@ -13,7 +13,9 @@ tests-common = $(TEST_DIR)/selftest.flat
 tests-common += $(TEST_DIR)/spinlock-test.flat
 tests-common += $(TEST_DIR)/tlbflush-test.flat
 
-all: test_cases
+utils-common = $(TEST_DIR)/utils/kvm-query
+
+all: test_cases utils
 
 ##################################################################
 phys_base = $(LOADADDR)
@@ -58,6 +60,9 @@ FLATLIBS = $(libcflat) $(LIBFDT_archive) $(libgcc) $(libeabi)
 $(libeabi): $(eabiobjs)
 	$(AR) rcs $@ $^
 
+$(TEST_DIR)/utils/%: $(TEST_DIR)/utils/%.c
+	$(CC) -std=gnu99 -o $@ $^
+
 arm_clean: libfdt_clean asm_offsets_clean
 	$(RM) $(TEST_DIR)/*.{o,flat,elf} $(libeabi) $(eabiobjs) \
 	      $(TEST_DIR)/.*.d lib/arm/.*.d
@@ -69,6 +74,7 @@ tests_and_config = $(TEST_DIR)/*.flat $(TEST_DIR)/unittests.cfg
 generated_files = $(asm-offsets)
 
 test_cases: $(generated_files) $(tests-common) $(tests)
+utils: $(utils-common)
 
 $(TEST_DIR)/selftest.elf: $(cstart.o) $(TEST_DIR)/selftest.o
 $(TEST_DIR)/spinlock-test.elf: $(cstart.o) $(TEST_DIR)/spinlock-test.o
-- 
2.5.0