Re: [PATCH 62/62] x86/sev-es: Add NMI state tracking

[Joerg Roedel]

On Tue, Feb 11, 2020 at 02:50:29PM -0800, Andy Lutomirski wrote:
> On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@xxxxxxxxxx> wrote:
> This patch is overcomplicated IMO.  Just do the magic incantation in C
> from do_nmi or from here:
> 
>         /*
>          * For ease of testing, unmask NMIs right away.  Disabled by
>          * default because IRET is very expensive.
> 
> If you do the latter, you'll need to handle the case where the NMI
> came from user mode.
> 
> The ideal solution is do_nmi, I think.
> 
> if (static_cpu_has(X86_BUG_AMD_FORGOT_ABOUT_NMI))
>   sev_es_unmask_nmi();
> 
> Feel free to use X86_FEATURE_SEV_ES instead :)

Yeah, I also had that implemented once, but then changed it because I
thought that nested NMIs do not necessarily call into do_nmi(), which
would cause NMIs to stay blocked forever. I need to read through the NMI
entry code again to check if that can really happen.

Regards,

	Joerg