ppc/xive: Check V bit in TM_PULL_POOL_CTX

A context should be 'valid' when pulled from the thread interrupt
context registers.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20191115162436.30548-8-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/intc/xive.c

@@ -377,6 +377,11 @@ static uint64_t xive_tm_pull_os_ctx(XiveTCTX *tctx, hwaddr offset,
 
     qw1w2 = xive_tctx_get_os_cam(tctx, &nvt_blk, &nvt_idx, &vo);
 
+    if (!vo) {
+        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: pulling invalid NVT %x/%x !?\n",
+                      nvt_blk, nvt_idx);
+    }
+
     /* Invalidate CAM line */
     qw1w2_new = xive_set_field32(TM_QW1W2_VO, qw1w2, 0);
     xive_tctx_set_os_cam(tctx, qw1w2_new);