qemu-system-aarch64: Failed to retrieve host CPU features

[Vitaly Chikunov]

Hi,

I noticed that we starting to get many errors like this:

  qemu-system-aarch64: Failed to retrieve host CPU features
 
Where many is 1-2% per run, depends on host, host is Kunpeng-920, and
Linux kernel is v5.15.59, but it started to appear months before that.

strace shows in erroneous case:

  1152244 ioctl(9, KVM_CREATE_VM, 0x30)   = -1 EINTR (Interrupted system call)

And I see in target/arm/kvm.c:kvm_arm_create_scratch_host_vcpu:

    vmfd = ioctl(kvmfd, KVM_CREATE_VM, max_vm_pa_size);
    if (vmfd < 0) {
        goto err;
    }

Maybe it should restart ioctl on EINTR?

I don't see EINTR documented in ioctl(2) nor in Linux'
Documentation/virt/kvm/api.rst for KVM_CREATE_VM, but for KVM_RUN it
says "an unmasked signal is pending".

Thanks,