Re: [Xen-devel] [PATCH] aarch64: advertise the GIC system register interface

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 31 Oct 2017, Peter Maydell wrote:
> On 31 October 2017 at 17:01, Stefano Stabellini <sstabellini@xxxxxxxxxx> 
> wrote:
> > Fixing QEMU is harder than I expected. Would it be possible to update
> > id_aa64pfr0 at CPU reset time? Like cpu->id_aa64pfr0 |= 0x01000000; ?
> 
> At that point we've already called register_cp_regs_for_features(),
> which is where we read cpu->id_aa64pfr0 when we're creating the
> cpreg. So if you change it after that it's too late. But that
> function is called at CPU realize time, which is before we've
> created the GIC object...

What about something along the lines of

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 9e18b41..0851071 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1401,6 +1400,10 @@ static void machvirt_init(MachineState *machine)
             object_property_set_link(cpuobj, OBJECT(secure_sysmem),
                                      "secure-memory", &error_abort);
         }
+        if (vms->gic_version == 3) {
+            ARMCPU *cpu = ARM_CPU(cpuobj);
+            cpu->id_aa64pfr0 |= 0x01000000;
+        }
 
         object_property_set_bool(cpuobj, true, "realized", NULL);
         object_unref(cpuobj);

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