Messages in this thread |  | | Subject | Re: [PATCH 1/5] KVM: x86: avoid atomic operations on APICv vmentry | From | Nadav Amit <> | Date | Fri, 14 Oct 2016 12:44:53 -0700 |
| |
> On Oct 14, 2016, at 11:56 AM, Paolo Bonzini <pbonzini@redhat.com> wrote: >>> >>> for (i = 0; i <= 7; i++) { >>> - pir_val = xchg(&pir[i], 0); >>> - if (pir_val) >>> + pir_val = READ_ONCE(pir[i]); >> >> Out of curiosity, do you really need this READ_ONCE? > > The answer can only be "depends on the compiler's whims". :) > If you think of READ_ONCE as a C11 relaxed atomic load, then yes.
Hm.. So the idea is to make the code "race-free” in the sense that every concurrent memory access is done using READ_ONCE/WRITE_ONCE?
If that is the case, I think there are many other cases that need to be changed, for example apic->irr_pending and vcpu->arch.pv.pv_unhalted.
|  |