Thanks Avi, for the review.
On 04/29/2012 06:55 PM, Avi Kivity wrote:
On 04/23/2012 12:59 PM, Raghavendra K T wrote:
From: Srivatsa Vaddagiri<vatsa@xxxxxxxxxxxxxxxxxx>
KVM_HC_KICK_CPU allows the calling vcpu to kick another vcpu out of halt state.
The presence of these hypercalls is indicated to guest via
KVM_FEATURE_PV_UNHALT/KVM_CAP_PV_UNHALT.
#endif
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e216ba0..dad475b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -481,6 +481,10 @@ struct kvm_vcpu_arch {
u64 length;
u64 status;
} osvw;
+ /* pv related host specific info */
+ struct {
+ int pv_unhalted;
+ } pv;
};
'bool'. Or maybe push into vcpu->requests.
Ok. I think you meant
+ struct {
+ bool pv_unhalted;
+ } pv;
and as discussed in old series (V4), cleaner implementation having
vcpu request, would still need a flag to prevent vcpu hang, so back to
having one flag.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4044ce0..7fc9be6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2147,6 +2147,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_ASYNC_PF:
case KVM_CAP_GET_TSC_KHZ:
case KVM_CAP_PCI_2_3:
+ case KVM_CAP_PV_UNHALT:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
Redundant, since we can infer this from KVM_GET_SUPPORTED_CPUID. But
please indicate this in the documentation.
Ok. will mention that in documentation added for KVM_CAP_PV_UNHALT.
+/*
+ * kvm_pv_kick_cpu_op: Kick a vcpu.
+ *
+ * @apicid - apicid of vcpu to be kicked.
+ */
+static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid)
+{
+ struct kvm_vcpu *vcpu = NULL;
+ int i;
+
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (!kvm_apic_present(vcpu))
+ continue;
+
+ if (kvm_apic_match_dest(vcpu, 0, 0, apicid, 0))
+ break;
+ }
+ if (vcpu) {
+ /*
+ * Setting unhalt flag here can result in spurious runnable
+ * state when unhalt reset does not happen in vcpu_block.
+ * But that is harmless since that should soon result in halt.
+ */
+ vcpu->arch.pv.pv_unhalted = 1;
+ /* We need everybody see unhalt before vcpu unblocks */
+ smp_mb();
smp_wmb().
Done.
+ kvm_vcpu_kick(vcpu);
+ }
+}
+
/*
* hypercalls use architecture specific
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 42b7393..edf56d4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1500,6 +1500,14 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
prepare_to_wait(&vcpu->wq,&wait, TASK_INTERRUPTIBLE);
if (kvm_arch_vcpu_runnable(vcpu)) {
+ /*
+ * This is the only safe place to reset unhalt flag.
+ * otherwise it results in loosing the notification
+ * which eventually can result in vcpu hangs.
+ */
+ kvm_arch_vcpu_reset_pv_unhalted(vcpu);
+ /* preventing reordering should be enough here */
+ barrier();
kvm_make_request(KVM_REQ_UNHALT, vcpu);
break;
}
Hm, what about reusing KVM_REQ_UNHALT?
Yes, I had experimented this for some time without success.
For e.g. having
make_request(KVM_REQ_UNHALT, vcpu) directly from kick hypercall.
It would still need a flag. (did not get any alternative so far except
the workaround posted in V4) :(
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