KVM: selftests: Add helpers to read integer module params

Add helpers to read integer module params, which is painfully non-trivial
because the pain of dealing with strings in C is exacerbated by the kernel
inserting a newline.

Don't bother differentiating between int, uint, short, etc.  They all fit
in an int, and KVM (thankfully) doesn't have any integer params larger
than an int.

Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-24-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 9e5afc472c14268bbe629cb9c1baf6049b702457..070f250036fcbbdd68f51e7ee2a01e63e6e2362a 100644 (file)
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -259,6 +259,10 @@ bool get_kvm_param_bool(const char *param);
 bool get_kvm_intel_param_bool(const char *param);
 bool get_kvm_amd_param_bool(const char *param);
 
+int get_kvm_param_integer(const char *param);
+int get_kvm_intel_param_integer(const char *param);
+int get_kvm_amd_param_integer(const char *param);
+
 unsigned int kvm_check_cap(long cap);
 
 static inline bool kvm_has_cap(long cap)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index e066d584c65611b4da45b0312734c3fab7b3dcd6..9bafe44cb9786a8afb4dad7c11b30814cf29e15b 100644 (file)
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -51,13 +51,13 @@ int open_kvm_dev_path_or_exit(void)
        return _open_kvm_dev_path_or_exit(O_RDONLY);
 }
 
-static bool get_module_param_bool(const char *module_name, const char *param)
+static ssize_t get_module_param(const char *module_name, const char *param,
+                               void *buffer, size_t buffer_size)
 {
        const int path_size = 128;
        char path[path_size];
-       char value;
-       ssize_t r;
-       int fd;
+       ssize_t bytes_read;
+       int fd, r;
 
        r = snprintf(path, path_size, "/sys/module/%s/parameters/%s",
                     module_name, param);
@@ -66,11 +66,46 @@ static bool get_module_param_bool(const char *module_name, const char *param)
 
        fd = open_path_or_exit(path, O_RDONLY);
 
-       r = read(fd, &value, 1);
-       TEST_ASSERT(r == 1, "read(%s) failed", path);
+       bytes_read = read(fd, buffer, buffer_size);
+       TEST_ASSERT(bytes_read > 0, "read(%s) returned %ld, wanted %ld bytes",
+                   path, bytes_read, buffer_size);
 
        r = close(fd);
        TEST_ASSERT(!r, "close(%s) failed", path);
+       return bytes_read;
+}
+
+static int get_module_param_integer(const char *module_name, const char *param)
+{
+       /*
+        * 16 bytes to hold a 64-bit value (1 byte per char), 1 byte for the
+        * NUL char, and 1 byte because the kernel sucks and inserts a newline
+        * at the end.
+        */
+       char value[16 + 1 + 1];
+       ssize_t r;
+
+       memset(value, '\0', sizeof(value));
+
+       r = get_module_param(module_name, param, value, sizeof(value));
+       TEST_ASSERT(value[r - 1] == '\n',
+                   "Expected trailing newline, got char '%c'", value[r - 1]);
+
+       /*
+        * Squash the newline, otherwise atoi_paranoid() will complain about
+        * trailing non-NUL characters in the string.
+        */
+       value[r - 1] = '\0';
+       return atoi_paranoid(value);
+}
+
+static bool get_module_param_bool(const char *module_name, const char *param)
+{
+       char value;
+       ssize_t r;
+
+       r = get_module_param(module_name, param, &value, sizeof(value));
+       TEST_ASSERT_EQ(r, 1);
 
        if (value == 'Y')
                return true;
@@ -95,6 +130,21 @@ bool get_kvm_amd_param_bool(const char *param)
        return get_module_param_bool("kvm_amd", param);
 }
 
+int get_kvm_param_integer(const char *param)
+{
+       return get_module_param_integer("kvm", param);
+}
+
+int get_kvm_intel_param_integer(const char *param)
+{
+       return get_module_param_integer("kvm_intel", param);
+}
+
+int get_kvm_amd_param_integer(const char *param)
+{
+       return get_module_param_integer("kvm_amd", param);
+}
+
 /*
  * Capability
  *