xen: arm: Annotate source of ICC SGI register trapping

I was unable to find an ARMv8 ARM reference to this, so refer to the
GIC Architecture Specification instead.

ARMv8 ARM does cover other ways of trapping these accesses via
ICH_HCR_EL2 but we don't use those and they trap additional registers
as well.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Julien Grall <julien.grall@citrix.com>

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 6eb2331718989fa2e1dbc25603692854f4d77d80..47d6cef8a62b46142473af4e5fc2c587624afc04 100644 (file)
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2174,6 +2174,12 @@ static void do_sysreg(struct cpu_user_regs *regs,
             return inject_undef_exception(regs, hsr);
         break;
 
+    /*
+     * HCR_EL2.FMO or HCR_EL2.IMO
+     *
+     * ARMv8: GIC Architecture Specification (PRD03-GENC-010745 24.0)
+     *        Section 4.6.8.
+     */
     case HSR_SYSREG_ICC_SGI1R_EL1:
         if ( !vgic_emulate(regs, hsr) )
         {