On 04/24/2012 03:29 PM, Gleb Natapov wrote:
On Mon, Apr 23, 2012 at 03:29:47PM +0530, 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.
Signed-off-by: Srivatsa Vaddagiri<vatsa@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Suzuki Poulose<suzuki@xxxxxxxxxx>
Signed-off-by: Raghavendra K T<raghavendra.kt@xxxxxxxxxxxxxxxxxx>
---
[...]
+/*
+ * 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();
+ kvm_vcpu_kick(vcpu);
+ }
+}
This is too similar to kvm_irq_delivery_to_apic(). Why not reuse it. We
can use one of reserved delivery modes as PV delivery mode. We will
disallow guest to trigger it through apic interface, so this will not be
part of ABI and can be changed at will.
I think it is interesting ( Perhaps more reasonable way of doing it).
I am not too familiar with lapic source. So, pardon me if my questions
are stupid.
Something like below is what I deciphered from your suggestion which is
working.
kvm/x86.c
=========
kvm_pv_kick_cpu_op()
{
struct kvm_lapic_irq lapic_irq;
lapic_irq.shorthand = 0;
lapic_irq.dest_mode = 0;
lapic_irq.dest_id = apicid;
lapic_irq.delivery_mode = PV_DELIVERY_MODE;
kvm_irq_delivery_to_apic(kvm, 0, &lapic_irq );
}
kvm/lapic.c
==========
_apic_accept_irq()
{
...
case APIC_DM_REMRD:
result = 1;
vcpu->pv_unhalted = 1
smp_mb();
kvm_make_request(KVM_REQ_EVENT, vcpu);
kvm_vcpu_kick(vcpu);
break;
...
}
here using PV_DELIVERY_MODE = APIC_DM_REMRD, which was unused.
OR
1) Are you asking to remove vcpu->pv_unhalted flag and replace with an irq?
2) are you talking about some reserved fields in struct local_apic instead
of APIC_DM_REMRD what I have used above?
[ Honestly, arch/x86/include/asm/apicdef.h had too much of info to
digest :( ]
3) I am not sure about: disallow guest to trigger it through apic
interface part also.(mean howto?)
4) And one more question, So you think it takes care of migration part
(in case we are removing pv_unhalted flag)?
It would be helpful if you can give little more explanation/ pointer to
Documentation.
Ingo is keen to see whole ticketlock/Xen/KVM patch in one go.
and anyhow since this does not cause any ABI change, I hope you don't
mind if
I do only the vcpu->pv_unhalted change you suggested now [ having
pv_unhalted reset in vcpu_run if
you meant something else than code I have above ], so that whole series
get fair amount time for testing.
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