tests/ioctl_kvm_run.c: handle cpuid at the end of vcpu dentry

Since Linux 4.16, kernel appends the cpuid as suffix to the entry
for a kvm vcpu in /proc/$pid/fd like:

    anon_inode:kvm-vcpu:0

That was

    anon_inode:kvm-vcpu

This kernel change causes the test case failure on newer kernels.
Update the test to deal with the new name as well as the old one.

* tests/ioctl_kvm_run.c: Include unistd.h for using readlink(2).
(vcpu_dev_should_have_cpuid): New function for detecting whether
a proc entry for given fd has the cpuid suffix or not.
(main): Trim vcpu_dev to remove the cpuid suffix if needed.
(vcpu_dev): Remove const modifier.

diff --git a/tests/ioctl_kvm_run.c b/tests/ioctl_kvm_run.c
index 17946143079d8e9c422e113bbc83eebda0bd381e..e1bef579607126c32db3f88818ce7eddf38b7864 100644 (file)
--- a/tests/ioctl_kvm_run.c
+++ b/tests/ioctl_kvm_run.c
@@ -40,6 +40,7 @@
 # include <string.h>
 # include <sys/ioctl.h>
 # include <sys/mman.h>
+# include <unistd.h>
 # include <linux/kvm.h>
 
 static int
@@ -56,7 +57,7 @@ kvm_ioctl(int fd, unsigned long cmd, const char *cmd_str, void *arg)
 
 static const char dev[] = "/dev/kvm";
 static const char vm_dev[] = "anon_inode:kvm-vm";
-static const char vcpu_dev[] = "anon_inode:kvm-vcpu";
+static char vcpu_dev[] = "anon_inode:kvm-vcpu:0";
 static size_t page_size;
 
 extern const char code[];
@@ -165,6 +166,23 @@ run_kvm(const int vcpu_fd, struct kvm_run *const run, const size_t mmap_size,
        }
 }
 
+static int
+vcpu_dev_should_have_cpuid(int fd)
+{
+       int r = 0;
+       char *filename = NULL;
+       char buf[sizeof(vcpu_dev)];
+
+       if (asprintf(&filename, "/proc/%d/fd/%d", getpid(), fd) < 0)
+               error_msg_and_fail("asprintf");
+
+       if (readlink(filename, buf, sizeof(buf)) == sizeof(buf) - 1
+           && (memcmp(buf, vcpu_dev, sizeof(buf) - 1) == 0))
+               r = 1;
+       free(filename);
+       return r;
+}
+
 int
 main(void)
 {
@@ -208,6 +226,15 @@ main(void)
               (unsigned long) page_size, (unsigned long) page_size, mem);
 
        int vcpu_fd = KVM_IOCTL(vm_fd, KVM_CREATE_VCPU, NULL);
+       if (!vcpu_dev_should_have_cpuid(vcpu_fd))
+               /*
+                * This is an older kernel that doesn't place a cpuid
+                * at the end of the dentry associated with vcpu_fd.
+                * Trim the cpuid part of vcpu_dev like:
+                * "anon_inode:kvm-vcpu:0" -> "anon_inode:kvm-vcpu"
+                */
+               vcpu_dev[strlen (vcpu_dev) - 2] = '\0';
+
        printf("ioctl(%d<%s>, KVM_CREATE_VCPU, 0) = %d<%s>\n",
               vm_fd, vm_dev, vcpu_fd, vcpu_dev);