On Tue, Jun 27, 2023 at 02:12:37AM +1200, Kai Huang wrote:
> +/*
> + * Do the module global initialization if not done yet.
> + * It's always called with interrupts and preemption disabled.
> + */
> +static int try_init_module_global(void)
> +{
> + unsigned long flags;
> + int ret;
> +
> + /*
> + * The TDX module global initialization only needs to be done
> + * once on any cpu.
> + */
> + raw_spin_lock_irqsave(&tdx_global_init_lock, flags);
> +
> + if (tdx_global_initialized) {
> + ret = 0;
> + goto out;
> + }
> +
> + /* All '0's are just unused parameters. */
> + ret = seamcall(TDH_SYS_INIT, 0, 0, 0, 0, NULL, NULL);
> + if (!ret)
> + tdx_global_initialized = true;
> +out:
> + raw_spin_unlock_irqrestore(&tdx_global_init_lock, flags);
> +
> + return ret;
> +}
> +
> +/**
> + * tdx_cpu_enable - Enable TDX on local cpu
> + *
> + * Do one-time TDX module per-cpu initialization SEAMCALL (and TDX module
> + * global initialization SEAMCALL if not done) on local cpu to make this
> + * cpu be ready to run any other SEAMCALLs.
> + *
> + * Call this function with preemption disabled.
> + *
> + * Return 0 on success, otherwise errors.
> + */
> +int tdx_cpu_enable(void)
> +{
> + int ret;
> +
> + if (!platform_tdx_enabled())
> + return -ENODEV;
> +
> + lockdep_assert_preemption_disabled();
> +
> + /* Already done */
> + if (__this_cpu_read(tdx_lp_initialized))
> + return 0;
> +
> + /*
> + * The TDX module global initialization is the very first step
> + * to enable TDX. Need to do it first (if hasn't been done)
> + * before the per-cpu initialization.
> + */
> + ret = try_init_module_global();
> + if (ret)
> + return ret;
> +
> + /* All '0's are just unused parameters */
> + ret = seamcall(TDH_SYS_LP_INIT, 0, 0, 0, 0, NULL, NULL);
> + if (ret)
> + return ret;
And here you do *NOT* have IRQs disabled... so an IRQ can come in here
and do the above again.
I suspect that's a completely insane thing to have happen, but the way
the code is written does not tell me this and might even suggest I
should worry about it, per the above thing actually disabling IRQs.
> +
> + __this_cpu_write(tdx_lp_initialized, true);
> +
> + return 0;
> +}
