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:   Wed, 28 Jun 2023 12:53:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Borislav Petkov <bp@...en8.de>
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 03:38:35PM +0200, Peter Zijlstra wrote:

> That said; there is a tiny difference between:
> 
> ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2)
> 
> and
> 
> ALTERNATIVE(ALTERNATIVE(oldinst, newinst1, flag1),
> 	    newinst2, flag2)
> 
> and that is alt_instr::instrlen, when the inner alternative is the
> smaller, then the outer alternative will add additional padding that the
> inner (obviously) doesn't know about.

New version:

https://lkml.kernel.org/r/20230628104952.GA2439977%40hirez.programming.kicks-ass.net