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authorPaul Mackerras <paulus@ozlabs.org>2019-08-27 11:35:40 +1000
committerPaul Mackerras <paulus@ozlabs.org>2019-08-27 14:08:22 +1000
commitff42df49e75f053a8a6b4c2533100cdcc23afe69 (patch)
tree7bf50e32722cab25271162d8b9b5098ef8f53994 /arch/powerpc/kvm
parentd28eafc5a64045c78136162af9d4ba42f8230080 (diff)
KVM: PPC: Book3S HV: Don't lose pending doorbell request on migration on P9
On POWER9, when userspace reads the value of the DPDES register on a vCPU, it is possible for 0 to be returned although there is a doorbell interrupt pending for the vCPU. This can lead to a doorbell interrupt being lost across migration. If the guest kernel uses doorbell interrupts for IPIs, then it could malfunction because of the lost interrupt. This happens because a newly-generated doorbell interrupt is signalled by setting vcpu->arch.doorbell_request to 1; the DPDES value in vcpu->arch.vcore->dpdes is not updated, because it can only be updated when holding the vcpu mutex, in order to avoid races. To fix this, we OR in vcpu->arch.doorbell_request when reading the DPDES value. Cc: stable@vger.kernel.org # v4.13+ Fixes: 579006944e0d ("KVM: PPC: Book3S HV: Virtualize doorbell facility on POWER9") Signed-off-by: Paul Mackerras <paulus@ozlabs.org> Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Diffstat (limited to 'arch/powerpc/kvm')
-rw-r--r--arch/powerpc/kvm/book3s_hv.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 36d72e9faddf..f8975c620f41 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1678,7 +1678,14 @@ static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
*val = get_reg_val(id, vcpu->arch.pspb);
break;
case KVM_REG_PPC_DPDES:
- *val = get_reg_val(id, vcpu->arch.vcore->dpdes);
+ /*
+ * On POWER9, where we are emulating msgsndp etc.,
+ * we return 1 bit for each vcpu, which can come from
+ * either vcore->dpdes or doorbell_request.
+ * On POWER8, doorbell_request is 0.
+ */
+ *val = get_reg_val(id, vcpu->arch.vcore->dpdes |
+ vcpu->arch.doorbell_request);
break;
case KVM_REG_PPC_VTB:
*val = get_reg_val(id, vcpu->arch.vcore->vtb);