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runstate: skip initial CPU reset if reset is not actually possible

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Right now, the system reset is concluded by a call to
cpu_synchronize_all_post_reset() in order to sync any changes
that the machine reset callback applied to the CPU state.

However, for VMs with encrypted state such as SEV-ES guests (currently
the only case of guests with non-resettable CPUs) this cannot be done,
because guest state has already been finalized by machine-init-done notifiers.
cpu_synchronize_all_post_reset() does nothing on these guests, and actually
we would like to make it fail if called once guest has been encrypted.
So, assume that boards that support non-resettable CPUs do not touch
CPU state and that all such setup is done before, at the time of
cpu_synchronize_all_post_init().

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-03-18 17:45:56 -04:00
parent ab0c7fb22b
commit 08b2d15cdd
1 changed files with 14 additions and 1 deletions
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15
system/runstate.c
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@ -501,7 +501,20 @@ void qemu_system_reset(ShutdownCause reason)
default:
qapi_event_send_reset(shutdown_caused_by_guest(reason), reason);
}
cpu_synchronize_all_post_reset();
/*
* Some boards use the machine reset callback to point CPUs to the firmware
* entry point. Assume that this is not the case for boards that support
* non-resettable CPUs (currently used only for confidential guests), in
* which case cpu_synchronize_all_post_init() is enough because
* it does _more_ than cpu_synchronize_all_post_reset().
*/
if (cpus_are_resettable()) {
cpu_synchronize_all_post_reset();
} else {
assert(runstate_check(RUN_STATE_PRELAUNCH));
}
vm_set_suspended(false);
}