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    SubjectRe: [PATCH RFC V5 2/6] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

    Sorry for late reply,
    was on vacation for a week (without IMAP access :( )

    On 04/12/2012 05:36 AM, Marcelo Tosatti wrote:
    > On Fri, Mar 23, 2012 at 01:37:04PM +0530, Raghavendra K T wrote:
    >> From: Srivatsa Vaddagiri<vatsa@linux.vnet.ibm.com>
    [snip]
    >> @@ -1567,6 +1568,9 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
    >> prepare_to_wait(&vcpu->wq,&wait, TASK_INTERRUPTIBLE);
    >>
    >> if (kvm_arch_vcpu_runnable(vcpu)) {
    >> + vcpu->pv_unhalted = 0;
    >> + /* preventing reordering should be enough here */
    >> + barrier();
    >
    > Is it always OK to erase the notification, even in case an unrelated
    > event such as interrupt was the source of wakeup?


    Erasing notification is not good, But I think in this case,

    kvm_make_request(KVM_REQ_UNHALT, vcpu);

    below this would take care of the rest.

    >
    > It would be easier to verify that notifications are not lost with atomic
    >
    > test_and_clear(pv_unhalted).

    true, I 'll verify that (with pv_unhalt as atomic variable). my heart
    says current code is just fine, since we are about to unblock.

    >
    > Also x86 specific code should remain in arch/x86/kvm/
    >

    I agree. 'll have clear function in arch/x86/kvm and add stub to rest
    of the archs

    >



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