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KVM: PPC: Book3S HV: Don't let VCPU sleep if it has a doorbell pending

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It is possible, through a narrow race condition, for a VCPU to exit
the guest with a H_CEDE hypercall while it has a doorbell interrupt
pending.  In this case, the H_CEDE should return immediately, but in
fact it puts the VCPU to sleep until some other interrupt becomes
pending or a prod is received (via another VCPU doing H_PROD).

This fixes it by checking the DPDES (Directed Privileged Doorbell
Exception Status) bit for the thread along with the other interrupt
pending bits.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Paul Mackerras 2017-05-19 16:26:16 +10:00
parent 1bc3fe818c
commit 1da4e2f4fb
1 changed files with 22 additions and 3 deletions
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25
arch/powerpc/kvm/book3s_hv.c
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@ -675,6 +675,17 @@ static void kvmppc_create_dtl_entry(struct kvm_vcpu *vcpu,
vcpu->arch.dtl.dirty = true;
}
/* See if there is a doorbell interrupt pending for a vcpu */
static bool kvmppc_doorbell_pending(struct kvm_vcpu *vcpu)
{
int thr;
struct kvmppc_vcore *vc;
vc = vcpu->arch.vcore;
thr = vcpu->vcpu_id - vc->first_vcpuid;
return !!(vc->dpdes & (1 << thr));
}
static bool kvmppc_power8_compatible(struct kvm_vcpu *vcpu)
{
if (vcpu->arch.vcore->arch_compat >= PVR_ARCH_207)
@ -2672,6 +2683,15 @@ static void shrink_halt_poll_ns(struct kvmppc_vcore *vc)
vc->halt_poll_ns /= halt_poll_ns_shrink;
}
static bool kvmppc_vcpu_woken(struct kvm_vcpu *vcpu)
{
if (vcpu->arch.pending_exceptions || vcpu->arch.prodded ||
kvmppc_doorbell_pending(vcpu))
return true;
return false;
}
/*
* Check to see if any of the runnable vcpus on the vcore have pending
* exceptions or are no longer ceded
@ -2682,8 +2702,7 @@ static int kvmppc_vcore_check_block(struct kvmppc_vcore *vc)
int i;
for_each_runnable_thread(i, vcpu, vc) {
if (vcpu->arch.pending_exceptions || !vcpu->arch.ceded ||
vcpu->arch.prodded)
if (!vcpu->arch.ceded || kvmppc_vcpu_woken(vcpu))
return 1;
}
@ -2869,7 +2888,7 @@ static int kvmppc_run_vcpu(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
break;
n_ceded = 0;
for_each_runnable_thread(i, v, vc) {
if (!v->arch.pending_exceptions && !v->arch.prodded)
if (!kvmppc_vcpu_woken(v))
n_ceded += v->arch.ceded;
else
v->arch.ceded = 0;