On 06/12/17 20:52, Radim Krčmář wrote:
2017-12-05 10:16+0200, Liran Alon:
In case posted-interrupt was delivered to CPU while it is in host
(outside guest), then posted-interrupt delivery will be done by
calling sync_pir_to_irr() at vmentry after interrupts are disabled.
sync_pir_to_irr() will check if vmx->pi_desc.control ON bit and if
set, it will sync vmx->pi_desc.pir to IRR and afterwards update RVI to
ensure virtual-interrupt-delivery will dispatch interrupt to guest.
However, it is possible that L1 will receive a posted-interrupt while
CPU runs at host and is about to enter L2. In this case, the call to
sync_pir_to_irr() will indeed update the L1's APIC IRR but
vcpu_enter_guest() will then just resume into L2 guest without
re-evaluating if it should exit from L2 to L1 as a result of this
new pending L1 event.
To address this case, if sync_pir_to_irr() has a new L1 injectable
interrupt and CPU is running L2, we set KVM_REQ_EVENT.
This will cause vcpu_enter_guest() to run another iteration of
evaluating pending KVM requests and will therefore consume
KVM_REQ_EVENT which will make sure to call check_nested_events() which
will handle the pending L1 event properly.
Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f5074ec5701b..47bbb8b691e8 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9031,20 +9031,33 @@ static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
+ int prev_max_irr;
int max_irr;
WARN_ON(!vcpu->arch.apicv_active);
+
+ prev_max_irr = kvm_lapic_find_highest_irr(vcpu);
if (pi_test_on(&vmx->pi_desc)) {
pi_clear_on(&vmx->pi_desc);
+
/*
* IOMMU can write to PIR.ON, so the barrier matters even on UP.
* But on x86 this is just a compiler barrier anyway.
*/
smp_mb__after_atomic();
max_irr = kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
I think the optimization (partly livelock protection) is not worth the
overhead of two IRR scans for non-nested guests. Please make
kvm_apic_update_irr() return both prev_max_irr and max_irr in one pass.
OK. I will modify kvm_apic_update_irr().
+
+ /*
+ * If we are running L2 and L1 has a new pending interrupt
+ * which can be injected, we should re-evaluate
+ * what should be done with this new L1 interrupt.
+ */
+ if (is_guest_mode(vcpu) && (max_irr > prev_max_irr))
+ kvm_make_request(KVM_REQ_EVENT, vcpu);
We don't need anything from KVM_REQ_EVENT and only use it to abort the
VM entry, kvm_vcpu_exiting_guest_mode() is better for that.
Yes you are right. I will change to kvm_vcpu_exiting_guest_mode().
} else {
- max_irr = kvm_lapic_find_highest_irr(vcpu);
+ max_irr = prev_max_irr;
}
+
vmx_hwapic_irr_update(vcpu, max_irr);
We also should just inject the interrupt if L2 is run without
nested_exit_on_intr(), maybe reusing the check in vmx_hwapic_irr_update?
See next patch in series :)
Thanks.
Regards,
-Liran
