[Qemu-devel] [PATCH 1/1] KVM: Retry KVM_CREATE_VM on EINTR or EAGAIN

[thomas knych <thomaswk@google.com>]

Upstreaming this change from Android (https://android-review.googlesource.com/54211).

On heavily loaded machines with many VM instances we see KVM_CREATE_VM
failing with EINTR/EAGAIN retrying the system call greatly improves
reliability.

Signed-off-by: thomas knych <thomaswk@google.com>
---
 kvm-all.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kvm-all.c b/kvm-all.c
index 3937754..29787ae 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1442,8 +1442,14 @@ int kvm_init(void)
         nc++;
     }
 
-    s->vmfd = kvm_ioctl(s, KVM_CREATE_VM, 0);
+    do {
+        s->vmfd = kvm_ioctl(s, KVM_CREATE_VM, 0);
+    } while (s->vmfd < 0 && (-EINTR == s->vmfd || -EAGAIN == s->vmfd));
+
     if (s->vmfd < 0) {
+        fprintf(stderr, "ioctl(KVM_CREATE_VM) failed: %d %s\n", -s->vmfd,
+                strerror(-s->vmfd));
+
 #ifdef TARGET_S390X
         fprintf(stderr, "Please add the 'switch_amode' kernel parameter to "
                         "your host kernel command line\n");
-- 
1.8.5.1