KVM: arm64: Inject UNDEF for a register trap without accessor

Configuring a register trap without specifying an accessor function is
abviously a bug. Instead of calling die() when that happens, let's be a
bit more helpful and print the register encoding. Also inject an
undefined instruction exception in the guest, similar to other unhandled
register accesses.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Link: https://msgid.link/20251216103053.47224-3-alexandru.elisei@arm.com
Signed-off-by: Oliver Upton <oupton@kernel.org>

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index c8fd7c6a12a13f294ea4bf92dbd1b23f1c880c49..88a57ca36d96c0675fbdaba680645f57cf06261c 100644 (file)
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -4668,7 +4668,10 @@ static void perform_access(struct kvm_vcpu *vcpu,
         * that we don't know how to handle. This certainly qualifies
         * as a gross bug that should be fixed right away.
         */
-       BUG_ON(!r->access);
+       if (!r->access) {
+               bad_trap(vcpu, params, r, "register access");
+               return;
+       }
 
        /* Skip instruction if instructed so */
        if (likely(r->access(vcpu, params, r)))