KVM: PPC: Book3S HV Nested: Fix nested HFSCR being clobbered with multiple vCPUs

The L0 is storing HFSCR requested by the L1 for the L2 in struct
kvm_nested_guest when the L1 requests a vCPU enter L2. kvm_nested_guest
is not a per-vCPU structure. Hilarity ensues.

Fix it by moving the nested hfscr into the vCPU structure together with
the other per-vCPU nested fields.

Fixes: 8b210a880b35 ("KVM: PPC: Book3S HV Nested: Make nested HFSCR state accessible")
Cc: stable@vger.kernel.org # v5.15+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220122105530.3477250-1-npiggin@gmail.com
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index d1817cd..84c89f0 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1816,7 +1816,6 @@ static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu,
 
 static int kvmppc_handle_nested_exit(struct kvm_vcpu *vcpu)
 {
-	struct kvm_nested_guest *nested = vcpu->arch.nested;
 	int r;
 	int srcu_idx;
 
@@ -1922,7 +1921,7 @@ static int kvmppc_handle_nested_exit(struct kvm_vcpu *vcpu)
 		 * it into a HEAI.
 		 */
 		if (!(vcpu->arch.hfscr_permitted & (1UL << cause)) ||
-					(nested->hfscr & (1UL << cause))) {
+				(vcpu->arch.nested_hfscr & (1UL << cause))) {
 			vcpu->arch.trap = BOOK3S_INTERRUPT_H_EMUL_ASSIST;
 
 			/*