linux-kernel - [tip: x86/asm] x86/ioperm: Use atomic64_inc_return() in ksys

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Message-ID: <174033533094.10177.10012973191295330448.tip-bot2@tip-bot2>
Date: Sun, 23 Feb 2025 18:28:50 -0000
From: "tip-bot2 for Uros Bizjak" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>, Ingo Molnar <mingo@...nel.org>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/asm] x86/ioperm: Use atomic64_inc_return() in ksys_ioperm()

The following commit has been merged into the x86/asm branch of tip:

Commit-ID:     dc8bd769e70ecae0916bf1b05acad6120c6bd6f0
Gitweb:        https://git.kernel.org/tip/dc8bd769e70ecae0916bf1b05acad6120c6bd6f0
Author:        Uros Bizjak <ubizjak@...il.com>
AuthorDate:    Sun, 23 Feb 2025 17:13:38 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Sun, 23 Feb 2025 19:18:18 +01:00

x86/ioperm: Use atomic64_inc_return() in ksys_ioperm()

Use atomic64_inc_return(&ref) instead of atomic64_add_return(1, &ref)
to use optimized implementation on targets that define
atomic_inc_return() and to remove now unneeded initialization of the
%eax/%edx register pair before the call to atomic64_inc_return().

On x86_32 the code improves from:

 1b0:    b9 00 00 00 00           mov    $0x0,%ecx
            1b1: R_386_32    .bss
 1b5:    89 43 0c                 mov    %eax,0xc(%ebx)
 1b8:    31 d2                    xor    %edx,%edx
 1ba:    b8 01 00 00 00           mov    $0x1,%eax
 1bf:    e8 fc ff ff ff           call   1c0 <ksys_ioperm+0xa8>
            1c0: R_386_PC32    atomic64_add_return_cx8
 1c4:    89 03                    mov    %eax,(%ebx)
 1c6:    89 53 04                 mov    %edx,0x4(%ebx)

to:

 1b0:    be 00 00 00 00           mov    $0x0,%esi
            1b1: R_386_32    .bss
 1b5:    89 43 0c                 mov    %eax,0xc(%ebx)
 1b8:    e8 fc ff ff ff           call   1b9 <ksys_ioperm+0xa1>
            1b9: R_386_PC32    atomic64_inc_return_cx8
 1bd:    89 03                    mov    %eax,(%ebx)
 1bf:    89 53 04                 mov    %edx,0x4(%ebx)

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20250223161355.3607-1-ubizjak@gmail.com
---
 arch/x86/kernel/ioport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index e2fab3c..6290dd1 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -144,7 +144,7 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 	 * Update the sequence number to force a TSS update on return to
 	 * user mode.
 	 */
-	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
+	iobm->sequence = atomic64_inc_return(&io_bitmap_sequence);
 
 	return 0;
 }