From: Suraj Jitindar Singh sjitindarsingh@gmail.com
commit 869537709ebf1dc865e75c3fc97b23f8acf37c16 upstream.
On POWER9 the decrementer can operate in large decrementer mode where the decrementer is 56 bits and signed extended to 64 bits. When not operating in this mode the decrementer behaves as a 32 bit decrementer which is NOT signed extended (as on POWER8).
Currently when reading a guest decrementer value we don't take into account whether the large decrementer is enabled or not, and this means the value will be incorrect when the guest is not using the large decrementer. Fix this by sign extending the value read when the guest isn't using the large decrementer.
Fixes: 95a6432ce903 ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests") Cc: stable@vger.kernel.org # v4.20+ Signed-off-by: Suraj Jitindar Singh sjitindarsingh@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kvm/book3s_hv.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3603,6 +3603,8 @@ int kvmhv_p9_guest_entry(struct kvm_vcpu
vcpu->arch.slb_max = 0; dec = mfspr(SPRN_DEC); + if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */ + dec = (s32) dec; tb = mftb(); vcpu->arch.dec_expires = dec + tb; vcpu->cpu = -1;