xen/arm: ignore writes to GICD_ICACTIVER ... GICD_ICACTIVERN

Injecting a fault to the guest just because it is writing to one of the
GICD_ICACTIVER registers, which are part of the GICv2 and GICv3 specs,
is harsh. Additionally it causes recent linux kernels to fail to boot on
Xen.

Ignore writes to GICD_ICACTIVER ... GICD_ICACTIVERN instead, to solve
the boot issue and for backportability. However implementing the
registers properly might a better long term solution.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

xen/arch/arm/vgic-v2.c

@@ -494,11 +494,10 @@ static int vgic_v2_distr_mmio_write(struct vcpu *v, mmio_info_t *info,
         return 0;
 
     case VRANGE32(GICD_ICACTIVER, GICD_ICACTIVERN):
-        if ( dabt.size != DABT_WORD ) goto bad_width;
         printk(XENLOG_G_ERR
                "%pv: vGICD: unhandled word write %#"PRIregister" to ICACTIVER%d\n",
                v, r, gicd_reg - GICD_ICACTIVER);
-        return 0;
+        goto write_ignore_32;
 
     case VRANGE32(GICD_IPRIORITYR, GICD_IPRIORITYRN):
     {

xen/arch/arm/vgic-v3.c

@@ -621,11 +621,10 @@ static int __vgic_v3_distr_common_mmio_write(const char *name, struct vcpu *v,
         return 0;
 
     case VRANGE32(GICD_ICACTIVER, GICD_ICACTIVERN):
-        if ( dabt.size != DABT_WORD ) goto bad_width;
         printk(XENLOG_G_ERR
                "%pv: %s: unhandled word write %#"PRIregister" to ICACTIVER%d\n",
                v, name, r, reg - GICD_ICACTIVER);
-        return 0;
+        goto write_ignore_32;
 
     case VRANGE32(GICD_IPRIORITYR, GICD_IPRIORITYRN):
     {