Re: [Qemu-devel] [PULL 7/9] KVM: Retry KVM_CREATE_VM on EINTR

[Paolo Bonzini <pbonzini@redhat.com>]

Il 27/01/2014 14:44, Alexander Graf ha scritto:
>
> On 20.01.2014, at 15:44, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
>> From: 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 on this path:
>>
>> kvm_dev_ioctl_create_vm -> kvm_create_vm -> kvm_init_mmu_notifier -> mmu_notifier_register ->  do_mmu_notifier_register -> mm_take_all_locks
>>
>> which checks if any signals have been raised while it was attaining locks
>> and returns EINTR.  Retrying the system call greatly improves reliability.
>>
>> Cc: qemu-stable@nongnu.org
>> Signed-off-by: thomas knych <thomaswk@google.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>> kvm-all.c | 12 +++++++++---
>> 1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/kvm-all.c b/kvm-all.c
>> index 3937754..6df2ee1 100644
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -1442,16 +1442,22 @@ int kvm_init(void)
>>         nc++;
>>     }
>>
>> -    s->vmfd = kvm_ioctl(s, KVM_CREATE_VM, 0);
>> -    if (s->vmfd < 0) {
>> +    do {
>> +        ret = kvm_ioctl(s, KVM_CREATE_VM, 0);
>> +    } while (ret == -EINTR);
>> +
>> +    if (ret < 0) {
>> +        fprintf(stderr, "ioctl(KVM_CREATE_VM) failed: %d %s\n", -s->vmfd,
>
> Shouldn't this be -ret?

Yes.  Can you send a patch?

Paolo