On Mon, Aug 26, 2024, Manali Shukla wrote:
> >> +struct buslock_test {
> >> + unsigned char pad[126];
> >> + atomic_long_t val;
> >> +} __packed;
> >> +
> >> +struct buslock_test test __cacheline_aligned;
> >> +
> >> +static __always_inline void buslock_atomic_add(int i, atomic_long_t *v)
> >> +{
> >> + asm volatile(LOCK_PREFIX "addl %1,%0"
> >> + : "+m" (v->counter)
> >> + : "ir" (i) : "memory");
> >> +}
> >> +
> >> +static void buslock_add(void)
> >> +{
> >> + /*
> >> + * Increment a cache unaligned variable atomically.
> >> + * This should generate a bus lock exit.
> >
> > So... this test doesn't actually verify that a bus lock exit occurs. The userspace
> > side will eat an exit if one occurs, but there's literally not a single TEST_ASSERT()
> > in here.
>
> Agreed, How about doing following?
>
> + for (;;) {
> + struct ucall uc;
> +
> + vcpu_run(vcpu);
> +
> + if (run->exit_reason == KVM_EXIT_IO) {
> + switch (get_ucall(vcpu, &uc)) {
> + case UCALL_ABORT:
> + REPORT_GUEST_ASSERT(uc);
> + /* NOT REACHED */
> + case UCALL_SYNC:
> + break;
> + case UCALL_DONE:
> + goto done;
> + default:
> + TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
> + }
> + }
> +
> + TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_X86_BUS_LOCK);
I doubt this works, the UCALL_SYNC above will fallthrough to this assert. I
assume run->exit_reason needs a continue for UCALL_SYNC.
> + TEST_ASSERT_EQ(run->flags, KVM_RUN_X86_BUS_LOCK);
> + run->flags &= ~KVM_RUN_X86_BUS_LOCK;
No need, KVM should clear the flag if the exit isn't due to a bus lock.
> + run->exit_reason = 0;
Again, no need, KVM should take care of resetting exit_reason.
> + }
>
> - Manali
>
>
