target/arm/kvm: Retry KVM_CREATE_VM call if it fails EINTR
Occasionally the KVM_CREATE_VM ioctl can return EINTR, even though
there is no pending signal to be taken. In commit 94ccff13382055
we added a retry-on-EINTR loop to the KVM_CREATE_VM call in the
generic KVM code. Adopt the same approach for the use of the
ioctl in the Arm-specific KVM code (where we use it to create a
scratch VM for probing for various things).
For more information, see the mailing list thread:
https://lore.kernel.org/qemu-devel/8735e0s1zw.wl-maz@kernel.org/
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
The view in the thread seems to be that this is a kernel bug (because
in QEMU's case there shouldn't be a signal to be delivered at this
point because of our signal handling strategy); so I've adopted the
same "just retry-on-EINTR for this specific ioctl" approach that
commit 94ccff13 did, rather than, for instance, something wider like
"make kvm_ioctl() and friends always retry on EINTR".
v2: correctly check for -1 and errno is EINTR...
v3: really correctly check errno. This time for sure!
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index e5c1bd5..1e4de9b 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -79,7 +79,9 @@
if (max_vm_pa_size < 0) {
max_vm_pa_size = 0;
}
- vmfd = ioctl(kvmfd, KVM_CREATE_VM, max_vm_pa_size);
+ do {
+ vmfd = ioctl(kvmfd, KVM_CREATE_VM, max_vm_pa_size);
+ } while (vmfd == -1 && errno == EINTR);
if (vmfd < 0) {
goto err;
}