Mikhail Tyutin <m.tyu...@yadro.com> writes:
> TCG Plugin callback to notify plugins when interrupt is triggered for
> a vCpu. The plugin can optionally use this notification to see reason
> of aborted instruction execution.
>
> Signed-off-by: Mikhail Tyutin <m.tyu...@yadro.com>
> ---
> accel/tcg/cpu-exec.c | 5 +++++
> include/qemu/plugin-event.h | 1 +
> include/qemu/plugin.h | 4 ++++
> include/qemu/qemu-plugin.h | 12 +++++++++++-
> plugins/core.c | 12 ++++++++++++
> plugins/qemu-plugins.symbols | 1 +
> 6 files changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index c938eb96f8..9110f7e290 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
The biggest problem I have with this approach is we are adding to an
already overly complex exception/interrupt code in the main loop.
> @@ -750,6 +750,7 @@ static inline bool cpu_handle_exception(CPUState *cpu,
> int *ret)
> if (replay_exception()) {
> CPUClass *cc = CPU_GET_CLASS(cpu);
> qemu_mutex_lock_iothread();
> + qemu_plugin_vcpu_interrupt_cb(cpu);
> cc->tcg_ops->do_interrupt(cpu);
This is at least what we think of as a traditional IRQ. Something that
interrupts the flow of the processor and after some target specific
processing goes somewhere else.
> qemu_mutex_unlock_iothread();
> cpu->exception_index = -1;
> @@ -829,6 +830,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
> /* Do nothing */
> } else if (interrupt_request & CPU_INTERRUPT_HALT) {
> replay_interrupt();
> + qemu_plugin_vcpu_interrupt_cb(cpu);
> cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
> cpu->halted = 1;
This isn't really an interrupt - its used by a selection of the various
architectures to bring the vCPU to a halted state. However it's not the
only way to halt the CPU as grepping for "->halted = 1;" will show you.
If we successfully halt we'll eventually end up calling:
qemu_plugin_vcpu_idle_cb()
> cpu->exception_index = EXCP_HLT;
> @@ -840,6 +842,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
> X86CPU *x86_cpu = X86_CPU(cpu);
> CPUArchState *env = &x86_cpu->env;
> replay_interrupt();
> + qemu_plugin_vcpu_interrupt_cb(cpu);
> cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
> do_cpu_init(x86_cpu);
> cpu->exception_index = EXCP_HALTED;
This is some x86 specific hack that we've not managed to find a sensible
way to excise out of the common code.
> @@ -849,6 +852,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
> #else
> else if (interrupt_request & CPU_INTERRUPT_RESET) {
> replay_interrupt();
> + qemu_plugin_vcpu_interrupt_cb(cpu);
> cpu_reset(cpu);
This again is not an IRQ really but another (minority) method for
generating a cold reset in the vCPU. There may be an argument to add a
plugin hook in cpu_reset() but I suspect most of the calls to it would
be artificial artefacts of the way to start and configure vCPUS as we
bring objects up.
> qemu_mutex_unlock_iothread();
> return true;
> @@ -866,6 +870,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
> if (need_replay_interrupt(interrupt_request)) {
> replay_interrupt();
> }
> + qemu_plugin_vcpu_interrupt_cb(cpu);
This may be an interrupt but we also may have restarted the loop via
cpu_loop_exit() so missing the rest of the logic. Some of these handlers
will also call cc->tcg_ops->do_interrupt(cpu) like above.
<snip>
>
> +void qemu_plugin_vcpu_interrupt_cb(CPUState *cpu)
> +{
> + plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_INTERRUPT);
> +}
> +
> void qemu_plugin_register_vcpu_idle_cb(qemu_plugin_id_t id,
> qemu_plugin_vcpu_simple_cb_t cb)
> {
> @@ -411,6 +417,12 @@ void
> qemu_plugin_register_vcpu_resume_cb(qemu_plugin_id_t id,
> plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_RESUME, cb);
> }
>
> +void qemu_plugin_register_vcpu_interrupt_cb(qemu_plugin_id_t id,
> + qemu_plugin_vcpu_simple_cb_t cb)
> +{
> + plugin_register_cb(id, QEMU_PLUGIN_EV_VCPU_INTERRUPT, cb);
> +}
> +
> void qemu_plugin_register_flush_cb(qemu_plugin_id_t id,
> qemu_plugin_simple_cb_t cb)
> {
> diff --git a/plugins/qemu-plugins.symbols b/plugins/qemu-plugins.symbols
> index 71f6c90549..c8621f9950 100644
> --- a/plugins/qemu-plugins.symbols
> +++ b/plugins/qemu-plugins.symbols
> @@ -30,6 +30,7 @@
> qemu_plugin_register_vcpu_mem_cb;
> qemu_plugin_register_vcpu_mem_inline;
> qemu_plugin_register_vcpu_resume_cb;
> + qemu_plugin_register_vcpu_interrupt_cb;
> qemu_plugin_register_vcpu_syscall_cb;
> qemu_plugin_register_vcpu_syscall_ret_cb;
> qemu_plugin_register_vcpu_tb_exec_cb;
When we add new callbacks we should at least use them in one of the
plugins to check they work.
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
