Re: [PATCH v6 1/2] x86/sev: Make sure IRQs are disabled while GHCB is active

[Peter Zijlstra]

On Wed, Jun 16, 2021 at 08:49:12PM +0200, Joerg Roedel wrote:

>  static void sev_es_ap_hlt_loop(void)
>  {
>  	struct ghcb_state state;
> +	unsigned long flags;
>  	struct ghcb *ghcb;
>  
> -	ghcb = sev_es_get_ghcb(&state);
> +	local_irq_save(flags);
> +
> +	ghcb = __sev_get_ghcb(&state);
>  
>  	while (true) {
>  		vc_ghcb_invalidate(ghcb);
> @@ -692,7 +704,9 @@ static void sev_es_ap_hlt_loop(void)
>  			break;
>  	}
>  
> -	sev_es_put_ghcb(&state);
> +	__sev_put_ghcb(&state);
> +
> +	local_irq_restore(flags);
>  }

I think this is broken, at this point RCU is quite dead on this CPU and
local_irq_save/restore include tracing and all sorts.

Also, shouldn't IRQs already be disabled by the time we get here?