linux-kernel - Re: [patch V9-1 13/39] x86/entry: Switch XEN/PV hypercall entry to IDTENTRY

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Date:   Tue, 26 May 2020 09:44:11 +0200
From:   Jürgen Groß <jgross@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Wei Liu <wei.liu@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Jason Chen CJ <jason.cj.chen@...el.com>,
        Zhao Yakui <yakui.zhao@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [patch V9-1 13/39] x86/entry: Switch XEN/PV hypercall entry to
 IDTENTRY

On 22.05.20 20:32, Thomas Gleixner wrote:
> Convert the XEN/PV hypercall to IDTENTRY:
> 
>    - Emit the ASM stub with DECLARE_IDTENTRY
>    - Remove the ASM idtentry in 64bit
>    - Remove the open coded ASM entry code in 32bit
>    - Remove the old prototypes
> 
> The handler stubs need to stay in ASM code as it needs corner case handling
> and adjustment of the stack pointer.
> 
> Provide a new C function which invokes the entry/exit handling and calls
> into the XEN handler on the interrupt stack if required.
> 
> The exit code is slightly different from the regular idtentry_exit() on
> non-preemptible kernels. If the hypercall is preemptible and need_resched()
> is set then XEN provides a preempt hypercall scheduling function.
> 
> Move this functionality into the entry code so it can use the existing
> idtentry functionality.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Acked-by: Juergen Gross <jgross@...e.com>
Tested-by: Juergen Gross <jgross@...e.com>


Juergen