[Xen-devel] [PATCH v2 17/17] arm64: if trapping a read-from-write-only GICv3 access inject undef exception in guest

[Manish Jaggi <manish.jaggi@xxxxxxxxxx>]

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>
---
 xen/arch/arm/arm64/vgic-v3-sr.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/arm64/vgic-v3-sr.c b/xen/arch/arm/arm64/vgic-v3-sr.c
index 14276a4c92..d5dc8168c8 100644
--- a/xen/arch/arm/arm64/vgic-v3-sr.c
+++ b/xen/arch/arm/arm64/vgic-v3-sr.c
@@ -614,7 +614,11 @@ static void vgic_v3_write_eoir(struct cpu_user_regs *regs,
 
 static void vreg_emulate_eoi(struct cpu_user_regs *regs, const union hsr hsr)
 {
-    vgic_v3_write_eoir(regs, hsr);
+
+    if ( unlikely(hsr.sysreg.read) )
+        inject_undef_exception(regs, hsr);
+    else
+        vgic_v3_write_eoir(regs, hsr);
 }
 
 static void vgic_v3_read_apxrn(struct cpu_user_regs *regs,
-- 
2.14.1


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