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Re: [Xen-devel] [PATCH v2 for 4.5] xen/arm: Add support for GICv3 for domU

Hi Ian,

On 05/11/2014 10:24, Ian Campbell wrote:
@@ -30,6 +32,39 @@ long arch_do_domctl(struct xen_domctl *domctl, struct domain 

          return p2m_cache_flush(d, s, e);
+    case XEN_DOMCTL_arm_configure_domain:
+    {
+        uint8_t gic_version;
+        /*
+         * Xen 4.5: The vGIC is emulating the same version of the

No need to say "Xen 4.5" here, this comment is true until it is removed.
You could say "Currently the vGIC is..." or something if you wanted to
indicate that this is temporary.

Just saying temporary doesn't say anything about when this has been added and will be removed.

"Xen 4.5" gives explicitly the time and show that we want to remove soon.

+         * hardware GIC. Only the value XEN_DOMCTL_CONFIG_GIC_DEFAULT
+         * is allowed. The DOMCTL will return the actual version of the
+         * GIC.
+         */
+        if ( domctl->u.configuredomain.gic_version != 
+            return -EOPNOTSUPP;

I'm also tempted to suggest that we should accept gic_version == the hw
value, i.e. by moping the switch below up and including
         && domctl->u.configuredomain.gic_version != gic_version
in the condition.

I consider that explicitly asking for a version of the GIC in Xen 4.5 is invalid. The user should only be able to use the default GIC.

As the DOMCTL is not set in stone, the developer should not start to consider that XEN_DOMCTL_CONFIG_GIC_V{2,3} will be valid in the future.

+#define GUEST_GICV3_GICR0_BASE     0x03020000ULL    /* vCPU0 - vCPU15 */

Don't we only support 8 cpus today? I don't mind reserving space for
more, and I'd be pleasantly surprised if 16 actually worked ;-)

I just copied used the code of Vijay. I suspect we could easily bump the number supported VCPUs to 16. But I didn't test it.


Julien Grall

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