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Re: [Xen-devel] [PATCH v2] xen/events: remove event handling recursion detection



On 28.11.19 22:37, Boris Ostrovsky wrote:
On 11/28/19 3:45 AM, Juergen Gross wrote:
-
  static void __xen_evtchn_do_upcall(void)
  {
        struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
-       int cpu = get_cpu();
-       unsigned count;
+       int cpu = smp_processor_id();
do {
                vcpu_info->evtchn_upcall_pending = 0;
- if (__this_cpu_inc_return(xed_nesting_count) - 1)
-                       goto out;
-
                xen_evtchn_handle_events(cpu);
BUG_ON(!irqs_disabled()); - count = __this_cpu_read(xed_nesting_count);
-               __this_cpu_write(xed_nesting_count, 0);
-       } while (count != 1 || vcpu_info->evtchn_upcall_pending);
-
-out:
+               rmb(); /* Hypervisor can set upcall pending. */

virt_rmb() perhaps then?

Yes, that's better.


Juergen


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