linux-kernel - Re: [RESEND][PATCH 1/6] x86/bugs: Add asm helpers for executing VERW

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Message-ID: <20231025152449.w6xre33cs7tkex7k@desk>
Date:   Wed, 25 Oct 2023 08:27:54 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Andrew Cooper <andrew.cooper3@...rix.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, tony.luck@...el.com,
        ak@...ux.intel.com, tim.c.chen@...ux.intel.com,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kvm@...r.kernel.org,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        antonio.gomez.iglesias@...ux.intel.com,
        Alyssa Milburn <alyssa.milburn@...el.com>
Subject: Re: [RESEND][PATCH 1/6] x86/bugs: Add asm helpers for executing VERW

On Wed, Oct 25, 2023 at 09:22:55AM +0200, Peter Zijlstra wrote:
 
> I'm thinking you need to at the very least stay in a section that's
> actually still mapped with PTI :-)
> 
> .entry.text is the only thing that is reliably mapped with PTI (IIRC),
> some configs also get a chunk of the kernel image, but not all.
> 
> Something like the below should do I suppose.

Thanks, will do this with Andrew's improvements.

> ---
>  arch/x86/entry/entry.S | 15 +++++++++++++++