diff options
| author | Paul Mackerras <paulus@ozlabs.org> | 2019-08-27 11:35:40 +1000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-10-11 18:20:44 +0200 |
| commit | 30fbe0d380aa038b0a629bc9c7f1961d340cd83b (patch) | |
| tree | ad39c35a4567fdefc0dde05d6a3e4caf0f5ac547 /arch | |
| parent | 4faa7f05af75f6c74c8ce25259e0d034f87526db (diff) | |
KVM: PPC: Book3S HV: Don't lose pending doorbell request on migration on P9
commit ff42df49e75f053a8a6b4c2533100cdcc23afe69 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/powerpc/kvm/book3s_hv.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 08dd16208e18..3ae3e8d141e3 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1407,7 +1407,14 @@ 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); |