23 May
2025
23 May
'25
2:33 p.m.
On Fri, May 23, 2025, Sairaj Kodilkar wrote:
On 5/23/2025 5:22 AM, Sean Christopherson wrote:
+int main(int argc, char *argv[]) +{
- pthread_t racing_thread;
- int r, i;
- /* Create "full" VMs, as KVM_IRQFD requires an in-kernel IRQ chip. */
- vm1 = vm_create(1);
- vm2 = vm_create(1);
- WRITE_ONCE(__eventfd, kvm_new_eventfd());
- kvm_irqfd(vm1, 10, __eventfd, 0);
- r = __kvm_irqfd(vm1, 11, __eventfd, 0);
- TEST_ASSERT(r && errno == EBUSY,
"Wanted EBUSY, r = %d, errno = %d", r, errno);- r = __kvm_irqfd(vm2, 12, __eventfd, 0);
- TEST_ASSERT(r && errno == EBUSY,
"Wanted EBUSY, r = %d, errno = %d", r, errno);- kvm_irqfd(vm1, 11, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN);
- kvm_irqfd(vm1, 12, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN);
- kvm_irqfd(vm1, 13, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN);
- kvm_irqfd(vm1, 14, READ_ONCE(__eventfd), KVM_IRQFD_FLAG_DEASSIGN);
Hi Sean, I dont see any allocation for the GSI 13 and 14.. Is there any reason for the deassigning these two GSIs ?
Yes, KVM's rather bizarre ABI is that DEASSIGN is allowed even if the VM doesn't have a corresponding assigned irqfd. The reason I added these early DEASSIGN calls is so that there will be an easier-to-debug failure if KVM's behavior changes (the racing threads part of the test abuses KVM's ABI). I didn't add a comment because the helpers already have comments, but looking at this again, I agree that main() needs a better comment.