linux-kernel - Re: [PATCH V3 1/7] x86/entry: Use idtentry macro for entry_INT80

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Message-ID: <YjHqqskCnZDgN2NI@hirez.programming.kicks-ass.net>
Date:   Wed, 16 Mar 2022 14:48:26 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Joerg Roedel <jroedel@...e.de>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Jan Kiszka <jan.kiszka@...mens.com>
Subject: Re: [PATCH V3 1/7] x86/entry: Use idtentry macro for
 entry_INT80_compat

On Tue, Mar 15, 2022 at 03:39:43PM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <jiangshan.ljs@...group.com>
> 
> entry_INT80_compat is identical to idtentry macro except a special
> handling for %rax in the prolog.
> 
> Add the prolog to idtentry and use idtentry for entry_INT80_compat.

I'm struggling to see the Xen case. Currently it has:

> -	/* In the Xen PV case we already run on the thread stack. */
> -	ALTERNATIVE "", "jmp .Lint80_keep_stack", X86_FEATURE_XENPV

But idtentry's error_entry() does not have that afaict.