Re: [PATCH v4 63/75] x86/sev-es: Handle #DB Events

[Peter Zijlstra]

On Tue, Jul 14, 2020 at 02:09:05PM +0200, Joerg Roedel wrote:

> @@ -1028,6 +1036,16 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
>  	struct ghcb *ghcb;
>  
>  	lockdep_assert_irqs_disabled();
> +
> +	/*
> +	 * #DB is special and needs to be handled outside of the intrumentation_begin()/end().
> +	 * Otherwise the #VC handler could be raised recursivly.
> +	 */
> +	if (error_code == SVM_EXIT_EXCP_BASE + X86_TRAP_DB) {
> +		vc_handle_trap_db(regs);
> +		return;
> +	}
> +
>  	instrumentation_begin();

Wait what?! That makes no sense what so ever.