KVM: PPC: Book3S HV: Restore SPRG3 in kvmhv_p9_guest_entry()

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>

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index d56eded4a0916ecf0676cc06e02f25ff5151a4dc..bd68b3e59de51f580d8ffb61bf76c6e880f1916b 100644 (file)
--- 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 *vcpu, u64 time_limit,
        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();