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Re: [Xen-devel] [PATCH RFC V5 2/6] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks
- To: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
- From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
- Date: Tue, 17 Apr 2012 09:19:01 +0530
- Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxx>, KVM <kvm@xxxxxxxxxxxxxxx>, Gleb Natapov <gleb@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, X86 <x86@xxxxxxxxxx>, linux-doc@xxxxxxxxxxxxxxx, Alexander Graf <agraf@xxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Randy Dunlap <rdunlap@xxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>, Xen <xen-devel@xxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, Sasha Levin <levinsasha928@xxxxxxxxx>
- Delivery-date: Tue, 17 Apr 2012 03:49:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
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@xxxxxxxxxxxxxxxxxx>
[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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