hw/intc/arm_gicv3_kvm: Stop wrongly programming GICR_PENDBASER.PTZ bit

If LPIs are disabled, KVM will just ignore the GICR_PENDBASER.PTZ bit when
restoring GICR_CTLR.  Setting PTZ here makes littlt sense in "reduce GIC
initialization time".

And what's worse, PTZ is generally programmed by guest to indicate to the
Redistributor whether the LPI Pending table is zero when enabling LPIs.
If migration is triggered when the PTZ has just been cleared by guest (and
before enabling LPIs), we will see PTZ==1 on the destination side, which
is not as expected.  Let's just drop this hackish userspace behavior.

Also take this chance to refine the comment a bit.

Fixes: 367b9f52 ("hw/intc/arm_gicv3_kvm: Implement get/put functions")
Signed-off-by: NZenghui Yu <yuzenghui@huawei.com>
Message-id: 20200119133051.642-1-yuzenghui@huawei.com
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/intc/arm_gicv3_kvm.c

@@ -336,7 +336,10 @@ static void kvm_arm_gicv3_put(GICv3State *s)
     kvm_gicd_access(s, GICD_CTLR, &reg, true);
 
     if (redist_typer & GICR_TYPER_PLPIS) {
-        /* Set base addresses before LPIs are enabled by GICR_CTLR write */
+        /*
+         * Restore base addresses before LPIs are potentially enabled by
+         * GICR_CTLR write
+         */
         for (ncpu = 0; ncpu < s->num_cpu; ncpu++) {
             GICv3CPUState *c = &s->cpu[ncpu];
 
@@ -347,12 +350,6 @@ static void kvm_arm_gicv3_put(GICv3State *s)
             kvm_gicr_access(s, GICR_PROPBASER + 4, ncpu, &regh, true);
 
             reg64 = c->gicr_pendbaser;
-            if (!(c->gicr_ctlr & GICR_CTLR_ENABLE_LPIS)) {
-                /* Setting PTZ is advised if LPIs are disabled, to reduce
-                 * GIC initialization time.
-                 */
-                reg64 |= GICR_PENDBASER_PTZ;
-            }
             regl = (uint32_t)reg64;
             kvm_gicr_access(s, GICR_PENDBASER, ncpu, &regl, true);
             regh = (uint32_t)(reg64 >> 32);