From: Suraj Jitindar Singh sjitindarsingh@gmail.com
commit d724c9e54939a597592de3659541da11fc7aa112 upstream.
The sprgs are a set of 4 general purpose sprs provided for software use. SPRG3 is special in that it can also be read from userspace. Thus it is used on linux to store the cpu and numa id of the process to speed up syscall access to this information.
This register is overwritten with the guest value on kvm guest entry, and so needs to be restored on exit again. Thus restore the value on the guest exit path in kvmhv_p9_guest_entry().
Cc: stable@vger.kernel.org # v4.20+ Fixes: 95a6432ce9038 ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests")
Signed-off-by: Suraj Jitindar Singh sjitindarsingh@gmail.com Signed-off-by: Paul Mackerras paulus@ozlabs.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kvm/book3s_hv.c | 1 + 1 file changed, 1 insertion(+)
--- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3624,6 +3624,7 @@ int kvmhv_p9_guest_entry(struct kvm_vcpu vc->in_guest = 0;
mtspr(SPRN_DEC, local_paca->kvm_hstate.dec_expires - mftb()); + mtspr(SPRN_SPRG_VDSO_WRITE, local_paca->sprg_vdso);
kvmhv_load_host_pmu();