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

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