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| author | Christian Borntraeger <borntraeger@de.ibm.com> | 2015-07-28 13:03:05 (GMT) |
|---|---|---|
| committer | Christian Borntraeger <borntraeger@de.ibm.com> | 2015-07-30 11:11:13 (GMT) |
| commit | 586b7ccdb7143b6a9b975d2c6ad52b6ca5c162b9 (patch) | |
| tree | 6de1a65ddb32e31348b3223f21f3c6e7219f4ceb /arch/s390 | |
| parent | 0da029ed7ee5fdf49a2a0e14160c3e9999be9292 (diff) | |
| download | linux-586b7ccdb7143b6a9b975d2c6ad52b6ca5c162b9.tar.xz | |
KVM: s390: Fix hang VCPU hang/loop regression
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")
Diffstat (limited to 'arch/s390')
| -rw-r--r-- | arch/s390/kvm/kvm-s390.c | 4 |
1 files changed, 2 insertions, 2 deletions
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. |