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

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Date:   Tue, 12 May 2020 23:01:01 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     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>,
        Steven Rostedt <rostedt@...dmis.org>,
        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: [patch V5 02/38] x86/entry/64: Use native swapgs in
 asm_native_load_gs_index()

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)
 	FRAME_BEGIN
-	SWAPGS
+	swapgs
 .Lgs_change:
 	movl	%edi, %gs
 2:	ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE
-	SWAPGS
+	swapgs
 	FRAME_END
 	ret
 SYM_FUNC_END(asm_native_load_gs_index)
@@ -1057,7 +1057,7 @@ EXPORT_SYMBOL(asm_native_load_gs_index)
 	.section .fixup, "ax"
 	/* running with kernelgs */
 SYM_CODE_START_LOCAL_NOALIGN(.Lbad_gs)
-	SWAPGS					/* switch back to user gs */
+	swapgs					/* switch back to user gs */
 .macro ZAP_GS
 	/* This can't be a string because the preprocessor needs to see it. */
 	movl $__USER_DS, %eax