linux-kernel - Re: [EXTERNAL] Re: [PATCH 5/9] x86/hyperv: Use vmmcall to implement Hyper-V hypercall in sev-snp enlightened guest

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Date:   Tue, 27 Jun 2023 14:05:02 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Tianyu Lan <ltykernel@...il.com>, kys@...rosoft.com,
        haiyangz@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com,
        tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, daniel.lezcano@...aro.org,
        arnd@...db.de, michael.h.kelley@...rosoft.com,
        Tianyu Lan <tiala@...rosoft.com>, linux-arch@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com
Subject: Re: [EXTERNAL] Re: [PATCH 5/9] x86/hyperv: Use vmmcall to implement
 Hyper-V hypercall in sev-snp enlightened guest

On Tue, Jun 27, 2023 at 01:50:02PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 27, 2023 at 06:57:28PM +0800, Tianyu Lan wrote:
> 
> > > "There is no x86 SEV SNP feature(X86_FEATURE_SEV_SNP) flag
> 
> I'm sure we can arrange such a feature if we need it, this isn't rocket
> science. Boris?

https://lore.kernel.org/r/20230612042559.375660-7-michael.roth@amd.com

> This seems to work; it's a bit magical for having a nested ALTERNATIVE
> but the output seems correct (the outer alternative comes last in
> .altinstructions and thus has precedence). Sure the [thunk_target] input
> goes unsed in one of the alteratives, but who cares.

I'd like to avoid the nested alternative if not really necessary. I.e.,
a static_call should work here too no?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette