linux-kernel - Re: [patch V5 02/38] x86/entry/64: Use native swapgs in asm_native_load_gs

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Date:   Wed, 13 May 2020 08:34:51 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...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>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.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 V5 02/38] x86/entry/64: Use native swapgs in asm_native_load_gs_index()

Steven Rostedt <rostedt@...dmis.org> writes:
> On Tue, 12 May 2020 23:01:01 +0200
> Thomas Gleixner <tglx@...utronix.de> wrote:
>
>> When PARAVIRT_XXL is in use, then load_gs_index() uses
>> xen_load_gs_index() and (asm_))native_load_gs_index() is unused.
>> 
>> It's therefore pointless to use the paravirtualized SWAPGS implementation
>> in asm_native_load_gs_index(). Switch it to a plain swapgs.
>> 
>> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Juergen Gross <jgross@...e.com>
>> ---
>>  arch/x86/entry/entry_64.S |    6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>> 
>> --- a/arch/x86/entry/entry_64.S
>> +++ b/arch/x86/entry/entry_64.S
>> @@ -1043,11 +1043,11 @@ idtentry simd_coprocessor_error		do_simd
>>   */
>>  SYM_FUNC_START(asm_native_load_gs_index)
>
> Small nit, but I would just call this: asm_load_gs_index.
>
> The "native" word is usually reserved for functions that are for bare
> metal and have a paravirt counterpart. As there is a
> native_load_gs_index(), I don't envision a need for a paravirt version
> of the asm function.

Fair enough.