From: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
When enabled GICv4.1 on Kunpeng 920 platform with 6.4 kernel (preemptible
kernel), running a vm with 128 vcpus on 64 pcpu, sometimes vm is not booted
successfully, and we find there is a situation that doorbell interrupt will
not occur event if there is a pending interrupt.
In function kvm_vcpu_wfi(), the parameter of need_db is true for function
vgic_v4_put() which wants to tell GICv4 that we need doorbells to be
signalled if there is a pending interrupt.
But if there is a preemption before kvm_vcpu_halt (after preempt_enable()),
it will change the value of vpe->resident, which will make vgic_v4_put()
is called with need_db = false When calling function schedule().
Then after calling schedule(), doorbell interrupt will not occur even
if there is a pending interrupt.
We need to keep need_db always true for emulate Wait-For-Interrupt
behavior, so set need_db true in vgic_v4_put() if it is in the process of
emulating WFI.
kvm_vcpu_wfi
preempt_disable
...
vgic_v4_put(vcpu, true)
vpe->resident = 0
need_db = 1
preempt_enable
------------------------------------------> preemption occur
kvm_sched_out
vgic_v4_put(vcpu, false)
vpe->resident == 0 -> return 0 (do nothing)
...
<------------------------------------------ back
kvm_sched_in
vgic_v4_load
vpe->resident = 1
...
------------------------------------------- Continue
kvm_vcpu_halt
set vcpu thread INTERRUPTIBLE
schedule() ->
kvm_sched_out
vgic_v4_put(vcpu, false)
need_db = 0 (vcpu thread is not scheduled and doorbell interrupt
will not signalled even if there is a pending interrupt)
vpe->resident = 0
Signed-off-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
---
arch/arm64/kvm/vgic/vgic-v4.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
index c1c28fe..37152cf8 100644
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c
@@ -343,6 +343,9 @@ int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db)
if (!vgic_supports_direct_msis(vcpu->kvm) || !vpe->resident)
return 0;
+ if (vcpu->stat.generic.blocking == 1)
+ need_db = true;
+
return its_make_vpe_non_resident(vpe, need_db);
}
--
2.8.1
