| Message ID | 1438255366-25805-2-git-send-email-borntraeger@de.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 2078f92..f32f843 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1742,10 +1742,10 @@ static bool ibs_enabled(struct kvm_vcpu *vcpu) static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu) { - if (!vcpu->requests) - return 0; retry: kvm_s390_vcpu_request_handled(vcpu); + if (!vcpu->requests) + return 0; /* * We use MMU_RELOAD just to re-arm the ipte notifier for the * guest prefix page. gmap_ipte_notify will wait on the ptl lock.
commit 785dbef407d8 ("KVM: s390: optimize round trip time in request handling") introduced a regression. This regression was seen with CPU hotplug in the guest and switching between 1 or 2 CPUs. This will set/reset the IBS control via synced request. Whenever we make a synced request, we first set the vcpu->requests bit and then block the vcpu. The handler, on the other hand, unblocks itself, processes vcpu->requests (by clearing them) and unblocks itself once again. Now, if the requester sleeps between setting of vcpu->requests and blocking, the handler will clear the vcpu->requests bit and try to unblock itself (although no bit is set). When the requester wakes up, it blocks the VCPU and we have a blocked VCPU without requests. Solution is to always unset the block bit. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Fixes: 785dbef407d8 ("KVM: s390: optimize round trip time in request handling") --- arch/s390/kvm/kvm-s390.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)