[Xen-devel] [PATCH v3 17/17] arm64: if trapping a read-from-write-only GICv3 access inject undef exception in guest

[Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>]

This patch is ported to xen from linux commit:
e7f1d1eef482150a64a6e6ad8faf40f8f97eed67
KVM: arm64: Log an error if trapping a read-from-write-only GICv3 access

A read-from-write-only GICv3 access should UNDEF at EL1. But since
we're in complete paranoia-land with broken CPUs, let's assume the
worse and gracefully handle the case.

Signed-off-by: Manish Jaggi <manish.jaggi@xxxxxxxxxx>

diff --git a/xen/arch/arm/arm64/vgic-v3-sr.c b/xen/arch/arm/arm64/vgic-v3-sr.c
index ac39eb5e1d..1b36b104bc 100644
--- a/xen/arch/arm/arm64/vgic-v3-sr.c
+++ b/xen/arch/arm/arm64/vgic-v3-sr.c
@@ -792,6 +792,11 @@ bool vgic_v3_handle_cpuif_access(struct cpu_user_regs 
*regs)
 
     case HSR_SYSREG_ICC_EOIR0_EL1:
     case HSR_SYSREG_ICC_EOIR1_EL1:
+        if ( unlikely(is_read) )
+        {
+            ret = false;
+            goto end;
+        }
         fn = vgic_v3_write_eoir;
         break;
 
-- 
2.14.1


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