target/arm: Add support for VCPU event states

target/arm: Add support for VCPU event states

This patch extends the qemu-kvm state sync logic with support for
KVM_GET/SET_VCPU_EVENTS, giving access to yet missing SError exception.
And also it can support the exception state migration.

The SError exception states include SError pending state and ESR value,
the kvm_put/get_vcpu_events() will be called when set or get system
registers. When do migration, if source machine has SError pending,
QEMU will do this migration regardless whether the target machine supports
to specify guest ESR value, because if target machine does not support that,
it can also inject the SError with zero ESR value.

Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1538067351-23931-3-git-send-email-gengdongjiu@huawei.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>